Drug-induced photosensitivity

Drug-induced photosensitivity is an abnormal skin reaction that appears when a person takes or applies certain medications and subsequently is exposed to sunlight. Some drugs make the skin much more sensitive to ultraviolet (UV) radiation and even, in some cases, to visible light.

As a consequence, a sun exposure that would normally be well tolerated can cause a significant reaction.

There are two major types of photosensitivity: the phototoxic reaction, the most frequent, and the photoallergic reaction, much less common. Although both are related to sun exposure, they are different processes.

Some medications absorb ultraviolet radiation and trigger reactions in the skin.

Phototoxic reaction. It is the most frequent form. The medication directly increases the damage produced by solar radiation on the skin cells. It can affect anyone if they receive enough radiation. It generally appears a few hours after exposure.

Photoallergic reaction. It is much less frequent. In this case, sunlight modifies the medication and causes an immune system reaction similar to an allergy. It only occurs in predisposed people and usually appears between 24 and 72 hours after exposure.

Why had it never happened to me before? Because it depends on several factors: the medication used, the dose, the duration of treatment, the intensity of the sun and the skin type. It can appear even if you have previously taken the same medication without problems.

There are numerous medications capable of increasing sensitivity to the sun. Among the best known are:

• Antibiotics: doxycycline, minocycline, tetracyclines, ciprofloxacin, levofloxacin.
• Anti-inflammatories: ketoprofen, naproxen, piroxicam.
• Diuretics: hydrochlorothiazide, furosemide.
• Heart medications: amiodarone.
• Retinoids: isotretinoin, acitretin.
• Others: some antifungals, certain antidepressants, some antidiabetics, oncological drugs and immunosuppressants.

This does not mean that everyone who takes them will develop a reaction, but that the risk is higher.

The symptoms depend on the type of reaction.

Phototoxic reaction. It closely resembles an intense sunburn. It can produce redness, pain, a burning sensation, inflammation and blisters in the most intense cases. The lesions appear only on the sun-exposed areas.

Photoallergic reaction. It usually manifests as eczema. It can produce intense itching, redness, small blisters and peeling. Sometimes it can also spread to unexposed areas.

Diagnosis is based on the clinical history, the relationship between the medication and sun exposure and the examination of the lesions.

The doctor will review all of the patient's medication, including prescription medicines, over-the-counter products, creams, medicinal plants and supplements.

In some cases a phototest, a photopatch test (especially when a photoallergy is suspected) or a skin biopsy in unusual situations may be performed.

Treatment will depend on the severity of the reaction.

Stop or replace the medication. Whenever possible and only under medical indication. You should never stop a treatment on your own initiative.

Avoid sun exposure. While the lesions persist it is essential to avoid the sun.

Topical corticosteroids. They help to reduce inflammation.

Antihistamines. They can relieve itching when it is present.

Treatment of burns. In intense phototoxic reactions, measures similar to those used for sunburns may be necessary.

If you are taking a photosensitising medication:

• Use broad-spectrum sunscreen SPF 50+ every day.
• Reapply the sunscreen every two hours during exposure.
• Avoid the sun between 12:00 and 16:00.
• Wear a hat, sunglasses and protective clothing.
• Read the leaflet of new medications.
• Ask your doctor or pharmacist if you have doubts about the risk of photosensitivity.

In many cases it is possible to continue the treatment by adopting these measures.

Seek medical attention if you have extensive blisters, intense pain, lesions that worsen rapidly, fever, signs of infection, involvement of a large body surface or difficulty breathing and general symptoms.

You should also consult if the reaction appears repeatedly each time you take a particular medication.

• Myth: If I take a photosensitising medication I can never go out in the sun. Fact: In most cases you can lead a normal life by following strict photoprotection measures.
• Myth: Only antibiotics produce photosensitivity. Fact: Many other medications can also cause it.
• Myth: If I use sunscreen there is no risk. Fact: Sunscreen reduces the risk, but does not eliminate it completely.
• Myth: I should stop the treatment as soon as a reaction appears. Fact: You should never stop a medication without first consulting the doctor who prescribed it.
• Myth: All eruptions after taking a medication are an allergy. Fact: Many reactions are phototoxic and do not involve an allergic mechanism.

• Some medications increase the skin's sensitivity to the sun.
• There are two main mechanisms: phototoxicity and photoallergy.
• Doxycycline, hydrochlorothiazide, amiodarone and retinoids are some of the medications best known for producing photosensitivity.
• Strict photoprotection significantly reduces the risk.
• Never stop a treatment without first consulting your doctor.
• In the case of an intense or repeated reaction, you should seek a medical assessment.