Health. Photosensitization: When Sun and Medication Don't Mix

Photosensitization, sometimes incorrectly referred to as "sun allergy," is an overreaction of the skin to the sun's rays. It can manifest as itching, redness, or skin inflammation.

In some cases, it can be triggered or aggravated by taking medication, turning your usual treatment into an unexpected trap.

Phototoxicity: an immediate reaction

Phototoxicity is the most common form of drug-induced photosensitization. It occurs rapidly, within hours of sun exposure. The skin reacts as if it has suffered a severe sunburn, sometimes with the appearance of painful blisters.

This reaction has two variants depending on the method of administration of the drug. If you apply a photosensitizing cream or ointment, only the treated areas will be affected.

This is called contact photosensitization. However, if you take medication orally or by injection, any area exposed to the sun may react because the product circulates throughout the body.

The intensity of the reaction depends on several factors: the strength of the sun, the type of medication, the dose taken, and skin type. People with fair skin are naturally more vulnerable, but even darker skin is not immune.

The good news? This reaction gradually disappears as soon as you stop taking the medication or avoid the sun.

Photoallergy: rarer but more persistent

Photoallergy is a more complex and fortunately rarer mechanism. It only occurs in predisposed individuals who have already been "sensitized" by previous exposure to a combination of medication and UV rays.

Once this sensitization is established, even minimal sun exposure can trigger a reaction, as long as the person continues their treatment. Unlike phototoxicity, the lesions are not limited to the exposed areas and can spread to covered parts of the body. These lesions are more similar to eczema or hives.

This form of photosensitization is more worrisome because it disappears slowly after stopping the drug and can sometimes persist for a long time.

The list of potentially photosensitizing medications is longer than you might think. First and foremost, it's important to know that photosensitizing medications have a distinctive symbol (a pictogram depicting a partially obscured sun within a red triangle) on their packaging to help patients easily identify them.

Among the most common culprits are certain antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs), antihistamines, antidepressants, diuretics, proton pump inhibitors (omeprazole, pantoprazole, etc.), angiotensin-converting enzyme (ACE) inhibitors, sedatives, statins, etc.

Topical treatments are not left out: certain acne products, antiseptics, antifungal treatments or anti-allergy creams can also cause problems.

A general rule emerges: drugs taken orally or injected more often cause phototoxicity, while products applied directly to the skin tend to trigger photoallergies.

How to protect yourself?

Prevention remains your best ally. Read your medication instructions carefully and don't hesitate to ask your pharmacist or doctor about the risks of photosensitization.

If you absolutely must be exposed to the sun while taking a risky treatment, increase your protection: high-factor sunscreen, covering clothing and avoiding the hottest hours.