MEDICATIONS AND THE SUN

Drug-Induced Photosensitivity: Causes, Types, and Prevention

Exposure to certain drugs, cosmetics, sunscreens, and even plants, in combination with ultraviolet (UV) rays, can lead to an abnormal skin reaction known as drug-induced photosensitivity. This reaction affects people of all ages and ethnicities and is primarily triggered by UVA rays rather than UVB rays responsible for sunburns. Tanning beds, emitting 95% UVA rays, can also induce such reactions.

There are two main types of photosensitivity reactions:

1. Phototoxic Reaction:

• UV rays activate photosensitizing drugs, causing direct damage to exposed skin.
• Results in a painful, exaggerated sunburn reaction, occurring within minutes to hours.
• Severity depends on drug concentration and UV exposure intensity.
• In severe cases, vesicles and bullae may develop.

2. Photoallergic Reaction:

• An immune response occurs when UV light alters the drug’s structure.
• Delayed reaction, manifesting as eczema or urticaria 24 to 72 hours post UV exposure.
• Often accompanied by itching and can spread to non-exposed areas.
• Requires a minimal amount of medication to trigger a reaction.
• Mainly caused by topically applied products on the skin rather than oral or injected products.

Treatment and Prevention:

• Prevention is crucial for protection against photosensitivity reactions.
• Avoid sun exposure, especially between 10 a.m. and 4 p.m.
• Refrain from using tanning beds as they emit artificial UV rays.
• Wear anti-UV sunglasses, protective clothing, and a wide-brimmed hat.
• Use sunscreen with SPF 30 or higher and broad-spectrum UVA protection.
• Choose products with the Canadian Dermatology Association (CDA) logo.
• Consult a healthcare professional if a skin reaction occurs due to medication.
• When starting a new treatment, inquire about potential photosensitizing effects and preventive measures.

Prevention measures go beyond sunscreen, emphasizing the importance of protective clothing and minimizing UV exposure.