Q. Do medications react with sunlight?
A. Yes. There are two primary skin reactions that can occur with UV exposure: photo-toxic and photo-allergic.
Initially appearing as an exaggerated sunburn, photo-toxic reactions are believed to be caused when certain chemicals absorb energy from UV radiation, releasing it into the skin. Cell damage or death is the result. Photo-toxic substances make the skin ultra-sensitive to UV radiation, even if exposure to light is minimal. Painful reddening is most common, with blistering and pigmentation changes noticeable in some people. Photo-toxic reactions usually peak within 12–24 hours after exposure, although an early phase can appear as hive-like lesions, and some cases don’t show up for 72 hours. Once the reaction passes, skin damage, including discoloration and redness, can remain.
Medications and other substances that can cause photo-toxicity to include (for a complete list, including drug tradenames, see https://www.dhs.wisconsin.gov/radiation/medications.htm):
- Antihistamines
- Coal tar and derivatives
- Contraceptives, oral and estrogens
- Non-Steroidal Anti-Inflammatories
- Phenothiazines
- Psoralens
- Sulfonamides
- Sulfoylureas
- Thiazide Diuretics
- Tetracyclines
- Tricyclic Antidepressants
In his book Skin Secrets: The medical facts versus the beauty fiction (Collins & Brown Limited, London, England, 1999), Nicholas Lowe, MD, emeritus professor of dermatology at the University of California at Los Angeles School of Medicine and a senior lecturer in dermatology at University College in London, warns that other chemicals in the environment, such as arsenic, petrochemicals, and benzene dyes are photo-toxic. According to Lowe, when these chemicals are combined with UV rays, “they become poisonous and in some cases cause damage to deoxyribonucleic acid (DNA). These chemicals directly damage cellular DNA throughout the body and can predispose cells to cancerous changes.”
Photo-allergic reactions are rarer than photo-toxic reactions and affect the body’s immune system. They occur when UV light chemically alters medications or other substances on the skin’s surface, creating a new compound that triggers antibodies in the blood. Look for oozing, weeping, crusting, and itchy skin. Symptoms can show up in pre-sensitized individuals within 20 seconds after exposure, although the average time is 24–48 hours. Maximum inflammation usually peeks within 72 hours, with the whole episode over in 10–14 days. But don’t be fooled by the time limit. After the reaction is over and the substance is no longer present, photo-toxic skin eruptions can persist, sometimes as long as 20 years after the event. On the other hand, some people only react once to a substance, even with repeated exposures.
The most common photo-allergic substances include antibiotics, antifungals, antihistamines, diuretics, oral hypoglycemic agents, tranquilizers, and fragrances.
Since photo-toxicity and photo-allergies appear to be triggered more by UVA radiation than UVB, it is wise to wear an SPF 30-50 containing UVA-specific sunscreens when taking photo-reactive drugs. Parsol 1789 (avobenzone) and zinc oxide are most effective in this range of radiation. These sunscreens should be worn wherever skin is exposed to light, regardless of the time of year. Since UVA penetrates glass, they should be worn while flying, driving, and even indoors when sitting near a window. Of course, the best solution is to cover up. Wear tightly woven sun protective clothing and stay out of the sun as much as possible.
While light-skinned people are more susceptible to photosensitivity, those with dark skin are not immune to reactions. People with HIV or lupus erythematosus are at a much higher risk of UV sensitivity. UV exposure also can worsen autoimmune diseases, such as lupus and rheumatoid arthritis, and aggravate eczema, herpes, psoriasis, and acne if they already exist.
With everything that can go wrong under the sun, it’s very important that you are aware of the medications that can cause reactions between UV radiation and the skin. If you see an esthetician or dermatologist, be sure to let them know if you’ve changed any part of your routine, including medications, since the last time you came in for an appointment.
