Can Medications Make You More Sensitive to Sun and Heat?

Many drugs can intensify the effects of hot weather and sun. Here's how to protect yourself.

A woman in a wide brimmed hat from behind on a bright sunny day Photo: Getty Images

Extreme summer heat is on the rise in the U.S., according to the Centers for Disease Control and Prevention. And extreme heat puts people at risk of heat-related illness.

Plenty of factors can increase your risk, including your age and underlying health conditions. It may surprise you to know that the side effects of many medications, including common over-the-counter drugs such as ibuprofen and allergy medications containing diphenhydramine, can also increase your sensitivity to heat. Another possibility: Some medications can make your skin more sensitive to sunlight.

“A lot of people take medications, particularly elderly people, but also a lot of other groups in the community,” says Kimberly Humphrey, MBBS, an emergency medicine physician and climate change and human health fellow at the Harvard T.H. Chan School of Public Health. “As we have more and more hot days, we’ll see more and more people who are affected, and are affected because of the medications that they are taking.”

How Meds Can Make You More Vulnerable to Heat

Drugs can increase your sensitivity to heat in a few ways.

Some can affect your body’s ability to regulate its own temperature, or limit your ability to perceive how hot you’re getting, so you might not realize you’re overheating, Humphrey says. Other drugs can alter people’s ability to redirect blood flow to the skin, which is a primary way the body cools itself off. 

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Medications can also increase your risk of dehydration. Some types of drugs, notably diuretics, increase urine output, which can make it more difficult to stay hydrated. 

When it comes to antidepressant and antipsychotic drugs, dehydration can increase their concentration in a person’s body to higher doses than intended, which can mean increased side effects, says Shaili Gandhi, PharmD, vice president of formulary operations at SingleCare, a drug discount company.

Drugs that can increase your sensitivity to heat include (though aren’t limited to):

  • Antidepressants: tricyclic antidepressants such as amitriptyline (Elavil), doxepin (Sinequan), and nortriptyline (Pamelor).
  • Antihistamines: diphenhydramine (Benadryl Allergy). 
  • Antipsychotic drugs: atypical antipsychotics such as olanzapine (Zyprexa) and risperidone (Risperdal), and conventional antipsychotics such as thioridazine.
  • High blood pressure drugs: thiazide diuretics such as chlorothiazide (Diuril) and hydrochlorothiazide (HydroDiuril).
  • Overactive-bladder treatments: anticholinergics such as oxybutynin (Ditropan, Oxytrol) and solifenacin (Vesicare).
  • Mood-stabilizing lithium medications.

How Meds Can Make You More Vulnerable to Sun

Some medications can make your skin more sensitive to sunlight, a reaction known as photosensitivity. Photosensitivity can manifest in a few different ways. Most commonly, it can lead to a rash that can look like a bad sunburn, and can appear within minutes of sun exposure.

In other cases, UV rays alter the structure of a drug such that your body treats it as an allergen. The result is a red, itchy, scaly rash that develops 24 hours to several days after you’ve been in the sun. 

Overall, these side effects are relatively rare, says Humphrey, but people should still be aware that they’re possible. 

Drugs that can increase your sensitivity to sunlight include (though aren’t limited to):

  • Acne and aging skin treatments: products containing salicylic acid and tretinoin (Retin-A, Renova).
  • Antibiotics: fluoroquinolone antibiotics such as ciprofloxacin (Cipro), sulfa antibiotics such as sulfadiazine, and tetracycline antibiotics such as doxycycline (Doryx).
  • Antidepressants: tricyclic antidepressants such as amitriptyline (Elavil), doxepin (Sinequan), and nortriptyline (Pamelor).
  • High blood pressure drugs: ACE inhibitors such as benazepril (Lotensin) and captopril (Capoten), angiotensin II receptor antagonists such as valsartan (Diovan), and thiazide diuretics such as chlorothiazide (Diuril) and hydrochlorothiazide (HydroDiuril).
  • Pain medications: ibuprofen (Advil, Motrin) and naproxen (Aleve, Naprosyn), and topical pain relievers such as diclofenac (Voltaren gel, Pennsaid).

Heat and Sun Can Damage Medications Themselves

Hot temperatures can cause problems for medications before you even take them. Heat can cause the coatings on some drugs to crack, melt, or peel, which could affect how quickly the medication is released inside your body, Gandhi says. In general, medications should be kept away from high temperatures and direct sunlight. It’s wise to treat them as you might treat raw meat from the grocery store—don’t leave them in the car while you do other errands. Or at least bring them in your bag with you if you have to do another errand after you stop at the pharmacy. 

Also, insulin needs to be refrigerated, and heat can damage other diabetes supplies, such as blood sugar monitors and test strips, according to the CDC. When you’re traveling, keep insulin and other medicines in a cooler (though not directly touching ice or an ice pack).

How to Protect Yourself

Though not everyone will experience an adverse reaction, if you do take one or more medications that can increase your sensitivity to sun and heat, the following safety strategies can minimize your risk: 

Know your meds. Ask your doctor or pharmacist whether any of the medications you use could cause sun or heat sensitivity. If so, find out what you can do to mitigate any potential for side effects during times of high heat. Humphrey advises doing so well in advance, before temperatures reach dangerously high levels.

Hydrate. Sip nonalcoholic liquids throughout the day, even if you don’t feel thirsty. If you take a diuretic or have a medical reason to limit fluid intake, ask your doctor how much you should drink.

Be sun-safe. Use sunscreen daily, reapply often, and cover up (think sun-protective clothing and a wide-brimmed hat) when you’re outdoors during the day.

Seek shade. Stay in the shade or avoid being outdoors when the sun’s rays are at their peak. As a rule of thumb, if your shadow is shorter than you are, the UV light is at its strongest. Also, avoid tanning beds. 

Stay cool. Try to limit outdoor activities to the morning or evening, and seek refuge in air-conditioned rooms when it’s sweltering.

Know the signs of heat illness. Early signs include dizziness, fatigue, nausea and vomiting, and increased thirst. If you notice such symptoms, cool yourself down by getting into air conditioning, and drink water. More severe signs of potential heat stroke (which can be fatal) include confusion or an otherwise altered mental state, slurred speech, and loss of consciousness. If you suspect heat stroke in someone, call 911 and then try to cool the person down with cold water or a wet cloth.

Because heat stroke can cause confusion, you may not be able to recognize it in yourself. This is why it can be helpful to establish a practice of check-ins with friends and neighbors, particularly including older or other vulnerable people. “It’s always really good to set something up where others can check in to make sure that person is okay,” Humphrey says. 

Catherine Roberts

As a science journalist, my goal is to empower consumers to make informed decisions about health products, practices, and treatments. I aim to investigate what works, what doesn't, and what may be causing actual harm when it comes to people's health. As a civilian, my passions include science fiction, running, Queens, and my cat. Follow me on Twitter: @catharob