Sunlight can trigger reactions in some individuals, often called “sun allergies.” These represent the body’s immune system responding unusually to sun exposure. A new or heightened sensitivity to sunlight can develop, ranging from mild to severe.
When Sun Exposure Becomes a Problem
Photosensitivity describes an abnormal skin reaction to sunlight. Unlike a typical sunburn, photosensitivity involves disproportionate reactions, even with minimal sun exposure, manifesting as rashes, bumps, or intense itching on sun-exposed areas. The skin’s response is an immune system reaction to UV-induced changes, not merely a burn.
Reactions often appear on intermittently sun-exposed areas, such as the neck, chest, arms, and lower legs. The immune system mistakenly identifies sun-altered skin components as foreign, triggering an inflammatory response and visible skin changes.
Common Forms of Sun Sensitivity
Several distinct conditions fall under sun sensitivity. Polymorphous Light Eruption (PLE) is the most frequently encountered type, affecting up to 20% of people. It typically presents as itchy or burning red patches, small bumps, or blisters that appear a few hours to days after sun exposure. These rashes commonly develop on the upper chest, front of the neck, and arms, often in spring or early summer when sun exposure increases.
Solar Urticaria is a less common but often immediate reaction, characterized by hives or welts on sun-exposed skin. These itchy, reddish spots typically emerge within minutes of sun exposure and usually resolve within an hour of moving out of the sun. While the face and hands might be less affected due to potential tolerance, other intermittently exposed areas can react intensely.
Photoallergic Reactions involve an immune response when UV light interacts with certain chemicals applied to the skin or ingested. This can lead to a rash, blisters, or red bumps that may appear one to three days after exposure. Unlike other forms of sun sensitivity, these reactions can sometimes extend to areas of skin not directly exposed to sunlight.
Factors Contributing to Development
Sun sensitivity can stem from internal and external factors. Genetic predisposition plays a role, with a family history of sun allergy increasing the likelihood for conditions like Polymorphous Light Eruption. Underlying health conditions can contribute, but are generally less common triggers for new-onset sensitivity.
External factors frequently contribute to sun sensitivity. Certain medications are well-known photosensitizers, making skin more susceptible to UV damage or triggering an immune response. Examples include some antibiotics (tetracyclines, fluoroquinolones), nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen, and diuretics. Retinoids can also increase sun sensitivity.
Topical products can also induce reactions. Ingredients in sunscreens, perfumes, and coal tar derivatives can become allergenic when exposed to UV light, leading to photoallergic reactions. Contact with plants containing furanocoumarins can cause phytophotodermatitis, a painful inflammatory reaction with redness, blistering, and discoloration. This reaction is not an immune response but a direct toxic effect, often appearing in streaked patterns.
Diagnosis and Living with Sun Sensitivity
If sun sensitivity is suspected, seek professional medical diagnosis. A doctor, often a dermatologist, will review symptoms, medical history, and current medications. To confirm diagnosis and identify the type, specialized tests like phototesting may be performed, involving exposing skin to controlled UV light to observe the reaction. Photopatch testing determines if a reaction is caused by a substance applied to the skin.
Managing sun sensitivity involves proactive prevention. Strict sun avoidance, especially during peak UV hours (10 a.m. to 4 p.m.), is recommended. Wear protective clothing like long sleeves and wide-brimmed hats, and consistently apply broad-spectrum sunscreen with a high SPF. Avoiding known triggers, such as problematic medications or topical products, is also crucial. For symptom relief, over-the-counter or prescription corticosteroids can be used for rashes, and antihistamines for itching; some individuals may also gradually build tolerance through controlled light exposure under medical supervision, a process called “hardening the skin.”