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Drug side effects are common, and often quite troublesome.

Major side effects, such as severe or even life-threatening allergic reactions, require immediate treatment and discontinuation of the drug. More minor symptoms may be tolerable when weighed against drug benefits. And sometimes, these go away on their own as the body gets used to the drug.

But there’s another type of side effect you hear much less about: ones that are beneficial. Though uncommon, they’re worth keeping in mind when you’re starting a new medicine.

Aren’t all side effects bad?

The term side effect is usually assumed to be a bad thing. And that’s typically true. But that leaves out the “good” side effects. Relatively little is published on this, so it’s not clear how common they are. But four notable examples include:

• Minoxidil (Rogaine, Gainextra, other brands). Developed in the 1970s for high blood pressure, this drug also increased hair growth in study subjects. What was initially considered a bothersome side effect eventually became its primary use: topical forms of this drug are commonly used to treat hair loss.
• Diphenhydramine (Benadryl or generic versions). This common treatment for allergic conditions has the side effect of drowsiness. For adults with allergy issues and trouble sleeping, the sedative effect can be helpful. Regular, long-term use of diphenhydramine is not recommended, as it may increase the risk of dementia.
• Sildenafil (Viagra or generic versions). Originally developed as a treatment for high blood pressure and angina, it didn’t take long for male users to realize the drug could trigger erections within 30 to 60 minutes. The makers of sildenafil recognized that under the right circumstances, this could be a highly beneficial side effect. In 1998 it was approved as a treatment for erectile dysfunction.
• Semaglutide (Ozempic, Wegovy, Rybelsus). This drug was developed to treat diabetes, but early users noticed reduced appetite and significant weight loss. Now, several formulations of these related drugs are approved for diabetes and/or weight loss.

In the best study I’ve read on the topic, researchers found more than 450 reports of serendipitous beneficial effects of various drugs since 1991. And that may be an underestimation, since report forms did not specifically ask for or label this type of side effect, according to the study authors.

Silver linings: Repurposing and repackaging drugs

While the discovery of helpful drugs can arise unexpectedly, drug developers are increasingly using a more intentional approach: using side effect profiles to look for new uses.

For example:

• A drug reported to cause reduced sweating as a side effect may be effective for hyperhidrosis, a condition marked by excessive sweating.
• Drugs reported to cause low blood pressure as a side effect might be effective treatments for high blood pressure (hypertension).
• New treatments for breast cancer may include older medicines that have a similar side effect profile as known anti-cancer drugs.

The availability of large side effect registries has made this method of identifying drugs for repurposing a more realistic option. So, even negative side effects can have a silver lining.

Bad side effects and the nocebo effect

While side effects can be positive, most are not. Medication side effects are a common reason people give for not taking prescribed drugs regularly. And adverse reactions to medicines prompt up to 8% of hospital admissions, according to one analysis.

To make matters worse, in some cases the expectation of side effects seems to make them more likely to occur. Called the nocebo effect, it increases the chances of experiencing a negative side effect and seems due, at least in part, to expectations. Contrast this with the placebo effect, where a sugar pill or another inactive treatment can lead to benefit.

The bottom line

Many people avoid taking medications because they fear possible side effects. That’s understandable. But not taking a medication can mean missing out on its benefits. And anticipation or expectation of side effects can increase the chances you’ll have them.

So, while it’s important to be aware of the most common side effects caused by the medicines you take, it’s also important not to overestimate your chances of experiencing them. And remember: there’s always a chance you’ll have a side effect you actually welcome.

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD

If you are trying to cut back on added sugar — and you should, because excess sugar increases risks for obesity, diabetes, and heart disease — you might be tempted by products advertised as low sugar, no sugar, or sugar-free.

Many contain familiar low-calorie sugar substitutes like aspartame or sucralose instead of sugar. And as you’re reading labels, you also may run across another ingredient: sugar alcohol, which is used in products like sugar-free cookies, candies, ice cream, beverages, and chewing gums. Are any of these sweeteners a better choice nutritionally? Dr. Frank Hu, professor of nutrition and epidemiology with the Harvard T.H. Chan School of Public Health, weighs in below.

Are low-calorie or no-calorie sweeteners any healthier than natural sugar?

Also known as artificial sweeteners or sugar substitutes, the list of low-calorie and no-calorie sweeteners you may see on product nutrition labels includes acesulfame-K, saccharin, sucralose, neotame, and advantame. These have a higher sweetness intensity per gram than natural sugar.

So far research on them is mixed, although some observational studies have found that beverages containing low-calorie sweeteners are associated with a higher risk for diabetes and weight gain.

What exactly are sugar alcohols and how can you spot them?

Sugar alcohols may have the most misleading name, as they are neither sugar nor alcohol, according to Dr. Hu. “They are a type of carbohydrate derived from fruits and vegetables, although most commercial sugar alcohols are synthetically produced.”

You can usually spot many sugar alcohols on ingredient lists by “-ol” at the ends of their names. Examples include sorbitol, xylitol, lactitol, mannitol, erythritol, and maltitol.

Are sugar alcohols any healthier than other sugar substitutes or natural sugar?

Here is a look at the pros and cons.

The upside of sugar alcohols

Sugar alcohols reside in the sweet spot between natural sugar and low-calorie sweeteners. They are not as overly sweet as sweeteners and don’t add too many extra calories like sugar.

“Sugar alcohols are about 40% to 80% as sweet as natural sugar, whereas artificial sweeteners like aspartame are about 200 times sweeter,” says Dr. Hu. “And they have about 25% to 75% fewer calories per gram than sugar.”

Another upside of sugar alcohols is that they break down slowly in the gut. Hence, your body only absorbs part of their overall carbohydrates. “This keeps your blood sugar and insulin levels from spiking as they do with sugar,” says Dr. Hu. “That makes them a useful sugar substitute for people with diabetes.”

The downside of sugar alcohols

The main downside to sugar alcohols is this: when taken in high amounts they can cause gastrointestinal (GI) problems, such as abdominal pain, diarrhea, or loose stools.

Because sugar alcohols are slowly digested, they have more time to feed bacteria in the gut, which can lead to fermentation and produce excess gas. Their slow digestion also can pull extra water into the colon and cause a laxative effect.

People’s tolerance for sugar alcohols depends on many factors, including body weight, health conditions, and the amount and types of sugar alcohols. “Individual differences in digestion and metabolism, gut microbiome composition, and dietary habits can also make a difference,” says Dr. Hu. “For these reasons, we recommend introducing sugar alcohols into your diet gradually and observing how your body responds.”

For people who experience GI symptoms caused by sugar alcohols, Dr. Hu says cutting back on the amount of foods and drinks made with them often can correct the problem. “Sugar alcohols are commonly found in sugar-free or low-carb products, so pay attention to food labels” he says. “Because different sugar alcohols can have different effects, it might be useful to identify specific types of sugar alcohols that cause GI side effects.”

Do sugar alcohols have health risks?

Possible long-term health risks of sugar alcohol are still being explored. A 2023 observational study found a link between using erythritol as an added sweetener and cardiovascular disease events, such as stroke and heart attack, in people with heart disease or who had risk factors like diabetes and high blood pressure. However, these findings have not been confirmed in subsequent studies.

“Sugar alcohols offer a healthier alternative to sugar because of their lower calorie content and reduced glycemic response, which is the effect food has on blood sugar levels,” says Dr. Hu. “But they also have potential drawbacks, especially for those with sensitive digestive systems, so it’s best to consume them in moderation as part of an overall healthy eating pattern.”

About the Author

Matthew Solan, Executive Editor, Harvard Men's Health Watch

Matthew Solan is the executive editor of Harvard Men’s Health Watch. He previously served as executive editor for UCLA Health’s Healthy Years and as a contributor to Duke Medicine’s Health News and Weill Cornell Medical College’s … See Full Bio View all posts by Matthew Solan

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

If you spend time outdoors — which we all should do, for all sorts of reasons — you are likely to encounter biting bugs. Most of the time the bites are just a nuisance. But besides the fact that sometimes they can be painful or itchy, bug bites can lead to illness — like Lyme disease from ticks, or Zika, malaria, or West Nile disease from mosquitoes. So preventing bites is a good idea for all of us, and certainly for children.

Simple precautions will help

Before talking about insect repellents, it’s important to remember that there are simple and effective precautions, nearly all of which don’t involve any chemicals. For example:

• Empty out any standing water outside your home. That’s where mosquitoes breed.
• Wear long-sleeved shirts and long pants if you are going to be in areas with lots of biting insects. If you treat clothes (and shoes and gear) with 0.5% permethrin, it can be helpful.
• Be aware that mosquitoes are most likely to be out at dusk and dawn, and plan activities accordingly.
• To avoid tick bites, avoid wooded and brushy areas and keep to the center of paths when you hike. Be sure to do a tick check when you come home — not just of all the people in your group, but also any pets or gear that came along. Taking a shower soon after arriving home can help with both tick checks and washing off any unattached ticks.

Make choices about insect repellent

Insect repellents can be very useful. Some are more effective than others, and some can have side effects, so it’s important to do your homework. The Environmental Protection Agency has a great interactive tool that can help you choose the best repellent for your particular situation.

The most effective repellent is DEET (N, N-diethyl-meta-toluamide). It works against both mosquitoes and ticks, and is definitely the go-to repellent if you really want or need to prevent bites. The higher the concentration, the longer it lasts: 10% will give you about two hours of coverage, while 30% can protect you for about five hours. The American Academy of Pediatrics (AAP) recommends not using more than 30% on kids, and not using any repellents on infants less than 2 months old.

The most common side effect is skin irritation, and if you ingest it (you never know with little kids) it can lead to nausea and vomiting. Eye irritation is possible, which is why you should never spray any repellent directly to the face, but rather put it on your hands and then carefully apply to the face. In very rare cases, like one in every 100 million users, DEET can lead to brain problems such as seizures if used in high doses. This is an incredibly rare side effect, and not something that should stop you from using it, especially if you are in an area with a lot of ticks, or an area with lots of disease-carrying mosquitoes.

Here are some alternatives with minimal to no side effects (eye irritation most common; avoid as noted above):

• oil of lemon eucalyptus, or PMD (the manmade alternative). This works nearly as well as DEET.
• picaridin, which works better against mosquitoes than ticks
• 2-undecanone
• IR-3535, the active ingredient in Avon products, although it is not very effective
• citronella, although it is even less effective.

Applying insect repellent — and sunscreen

Whatever you use, follow label directions and be sure that you are careful as you apply it to all exposed skin. It’s best to spray in an open area — and spray clothing too. Pump bottles and wipes with insect repellent may help you apply products carefully. Try to choose the best product for your situation so that you can apply it just once; the EPA tool is great for that. Don’t forget sunscreen; apply that first so your skin can absorb it.

The Centers for Disease Control and Prevention (CDC) has more information about applying insect repellent on children and preventing bites from mosquitoes and ticks.

Also visit the Harvard Health Publishing Lyme Wellness Initiative to learn about preventing –– or living with –– Lyme disease and other tick-borne illnesses.

About the Author

Claire McCarthy, MD, Senior Faculty Editor, Harvard Health Publishing

Claire McCarthy, MD, is a primary care pediatrician at Boston Children’s Hospital, and an assistant professor of pediatrics at Harvard Medical School. In addition to being a senior faculty editor for Harvard Health Publishing, Dr. McCarthy … See Full Bio View all posts by Claire McCarthy, MD

Over the course of a lifetime, as many as seven in 10 adults in the United States will directly experience or witness harrowing events. These include gun violence, car accidents, and other personal trauma; natural or human-made disasters, such as Hurricane Katrina and the 9/11 terrorist attacks; and military combat. And some — though not all — will experience post-traumatic stress disorder, or PTSD.

New guidelines released in 2024 can help guide effective treatment.

What is PTSD?

PTSD is a potentially debilitating mental health condition. It’s marked by recurrent, frightening episodes during which a person relives a traumatic event.

After a disturbing event, it’s normal to have upsetting memories, feel on edge, and have trouble sleeping. For most people, these symptoms fade over time. But when certain symptoms persist for more than a month, a person may be experiencing PTSD.

These symptoms include

• recurring nightmares or intrusive thoughts about the event
• feeling emotionally numb and disconnected
• withdrawing from people and certain situations
• being jumpy and on guard.

The National Center for PTSD offers a brief self-screening test online, which can help you decide whether to seek more information and help.

Who is more likely to experience PTSD?

Not everyone who experiences violence, disasters, and other upsetting events goes on to develop PTSD. However, military personnel exposed to combat in a war zone are especially vulnerable. About 11% to 20% of veterans who served in Iraq or Afghanistan have PTSD, according to the National Center for PTSD.

What about people who were not in the military? Within the general population, estimates suggest PTSD occurs in 4% of men and 8% of women — a difference at least partly related to the fact that women are more likely to experience sexual assault.

What are the new guidelines for PTSD treatment?

Experts from the U.S. Department of Veterans Affairs and Department of Defense collaborated on new guidelines for treating PTSD. They detailed the evidence both for and against specific therapies for PTSD.

Their findings apply to civilian and military personnel alike, says Dr. Sofia Matta, a psychiatrist at Harvard-affiliated Massachusetts General Hospital and senior director of medical services at Home Base, a nonprofit organization that provides care for veterans, service members, and their families.

The circle of care is widely drawn for good reason. “It’s important to recognize that PTSD doesn’t just affect the person who is suffering but also their families and sometimes, their entire community,” Dr. Matta says. The rise in mass shootings in public places and the aftermath of these events are a grim reminder of this reality, she adds.

Which treatment approaches are most effective for PTSD?

The new guidelines looked at psychotherapy, medications, nondrug therapies. Psychotherapy, sometimes paired with certain medicines, emerged as the most effective approach.

The experts also recommended not taking certain drugs due to lack of evidence or possible harm.

Which psychotherapies are recommended for PTSD?

The recommended treatment for PTSD, psychotherapy, is more effective than medication. It also has fewer adverse side effects and people prefer it, according to the guidelines.

Which type of psychotherapy can help? Importantly, the most effective therapies for people with PTSD differ from those for people with other mental health issues, says Dr. Matta.

Both cognitive processing therapy and prolonged exposure therapy were effective. These two therapies teach people how to evaluate and reframe the upsetting thoughts stemming from the traumatic experience. The guidelines also recommend mindfulness-based stress reduction, an eight-week program that includes meditation, body scanning, and simple yoga stretches.

Which medications are recommended for PTSD?

Some people with severe symptoms need medication to feel well enough to participate in therapy. “People with PTSD often don’t sleep well due to insomnia and nightmares, and the resulting fatigue makes it hard to pay attention and concentrate,” says Dr. Matta.

Three medicines commonly prescribed for depression and anxiety — paroxetine (Paxil), sertraline (Zoloft), and venlafaxine (Effexor) — are recommended. Prazosin (Minipress) may help people with nightmares, but the evidence is weak.

Which medications are not recommended for PTSD?

The guidelines strongly recommended not taking benzodiazepines (anti-anxiety drugs often taken for sleep). Benzodiazepines such as alprazolam (Xanax) and clonazepam (Klonopin) offer no proven benefits for people with PTSD. They have several potential harms, including negative cognitive changes and decreased effectiveness of PTSD psychotherapies.

What about cannabis, psychedelics, and brain stimulation therapies?

Right now, evidence doesn’t support the idea that cannabis helps ease PTSD symptoms. And there are possible serious side effects from the drug, such as cannabis hyperemesis syndrome (severe vomiting related to long-term cannabis use).

There isn’t enough evidence to recommend for or against psychedelic-assisted therapies such as psilocybin (magic mushrooms) and MDMA (ecstasy). “Because these potential therapies are illegal under federal law, the barriers for conducting research on them are very high,” says Dr. Matta. However, recent legislative reforms may make such studies more feasible.

Likewise, the evidence is mixed for a wide range of other nondrug therapies, such as brain stimulation therapies like repetitive transcranial magnetic stimulation or transcranial direct current stimulation.

About the Author

Julie Corliss, Executive Editor, Harvard Heart Letter

Julie Corliss is the executive editor of the Harvard Heart Letter. Before working at Harvard, she was a medical writer and editor at HealthNews, a consumer newsletter affiliated with The New England Journal of Medicine. She … See Full Bio View all posts by Julie Corliss

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

When a prostate-specific antigen (PSA) blood test produces an abnormal result, the next step is usually a prostate biopsy. A biopsy can confirm or rule out a cancer diagnosis, but it also has certain drawbacks. Prostate biopsies are invasive procedures with potential side effects, and they often detect low-grade, slow-growing tumors that may not need immediate treatment — or any treatment at all.

Researchers are exploring various strategies for avoiding unnecessary biopsies. Specialized magnetic resonance imaging (MRI) scans, for instance, can be useful for predicting if a man’s tumor is likely to spread. A blood test called the Prostate Health Index (PHI) measures various forms of PSA, and can help doctors determine if a biopsy is needed.

In April, researchers at the University of Michigan published results with a test that screens for prostate cancer in urine samples. Called the MyProstateScore 2.0 (MPS2) test, it looks for 18 different genes associated with high-grade tumors. “If you’re negative on this test, it’s almost certain that you don’t have aggressive prostate cancer,” said Dr. Arul Chinnaiyan, a professor of pathology and urology at the University, in a press release.

Gathering data and further testing

To create the test, Dr. Chinnaiyan and his colleagues first turned to publicly-available databases containing over 58,000 prostate cancer-associated genes. From that initial pool, they narrowed down to 54 genes that are uniquely overexpressed in cancers classified as Grade Group 2 (GG2) or higher. The Grade Group system ranks prostate cancers from GG1 (the least dangerous) to GG5 (the most dangerous).

The team tested those 54 genes against archived urine samples from 761 men with elevated PSA who were scheduled for biopsy. This effort yielded 18 genes that consistently correlated with high-grade cancer in the biopsy specimens. These genes now make up MPS2.

Then the team validated the test by performing MPS2 testing on over 800 archived urine samples collected by a national prostate cancer research consortium. Other researchers affiliated with that consortium assessed the new urine test’s results against patient records.

Interpreting the results

Study findings showed that MPS2 correctly identified 95% of the GG2 prostate cancers and 99% of cancers that were GG3 or higher. Test accuracy was further improved by incorporating estimates of the prostate’s size (or volume, as it’s also called).

According to the team’s calculations, use of the MPS2 would have reduced unnecessary biopsies by 37%. If volume was included in the measure, then 41% of biopsies would have been avoided. By comparison, just 26% of biopsies would have been avoided with the PHI.

Dr. Chinnaiyan and his co-authors emphasize that ruling out high-grade cancer with a urine test offers some advantages over MRI. The specialized multi-parametric MRI scans needed to assess high-grade cancer in men with elevated PSA aren’t always available in community settings, for instance. Moreover, the interpretation of mpMRI results can vary from one radiologist to another. Importantly, the MPS2 can be updated over time as new prostate-cancer genes are identified.

Commentary

Dr. Boris Gershman, a urologist at Harvard-affiliated Beth Israel Deaconess Medical Center in Boston, and a member of the advisory and editorial board for the Harvard Medical School Guide to Prostate Diseases, described the new study results as promising. “It does appear that the performance of the 18-gene urine test is better than PSA alone,” he says.

But Dr. Gershman adds that it will be important to consider how such a test will fit into the current two-stage approach for PSA screening, which entails prostate MRI when the PSA is abnormal. Where MRI delivers a yes/no result (meaning lesions that look suspicious for cancer are either present or not), the MPS2 provides numerical risk estimates ranging between 0% and 100%. “The challenge with clinical implementation of a continuous risk score is where to draw the line for biopsy,” Dr. Gershman says.

“This research is very encouraging, since many men in rural areas may not have access to prostate MRI machines or the added sophistication that is needed in interpreting these MRI scans,” says Dr. Marc Garnick, the Gorman Brothers Professor of Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center. “A widely available urine test may eventually help provide more precision in determining who should undergo a prostate biopsy, and may also help to assess the probability that a cancer is clinically significant and in need of treatment.”

About the Author

Charlie Schmidt, Editor, Harvard Medical School Annual Report on Prostate Diseases

Charlie Schmidt is an award-winning freelance science writer based in Portland, Maine. In addition to writing for Harvard Health Publishing, Charlie has written for Science magazine, the Journal of the National Cancer Institute, Environmental Health Perspectives, … See Full Bio View all posts by Charlie Schmidt

About the Reviewer

Marc B. Garnick, MD, Editor in Chief, Harvard Medical School Annual Report on Prostate Diseases; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Marc B. Garnick is an internationally renowned expert in medical oncology and urologic cancer. A clinical professor of medicine at Harvard Medical School, he also maintains an active clinical practice at Beth Israel Deaconess Medical … See Full Bio View all posts by Marc B. Garnick, MD