When It’s Not A Sunburn But A Sun Allergy

As it gets warmer and people start spending more time outside, I have more and more patients coming into my office and complaining of a "sun allergy."

A sun allergy is really a layman's term, which refers to a number of conditions when a rash occurs on skin that has been exposed to the sun. These are also referred to as photosensitive disorders or photodermatoses, and can be broadly categorised into the following medical terms: idiopathic photodermatoses, exogenous photodermatoses, photoexacerbated dermatoses, genetic photodermatoses, and metabolic photodermatoses. Sounds complicated, right?

Let’s break it down:

If, after spending a few hours in the sun, you develop an itchy red bumpy rash on your chest and arms, you likely have polymorphous light eruption (PMLE). Often when someone says they have a “sun allergy,” they are referring to this condition, which has rash-like symptoms. It is also one of the most common photodermatoses.

PMLE most frequently occurs in women between the ages of 20-40. Polymorphous refers to the fact that the rash can look different on people, but it mostly appears as pink or red bumps on the arms, chest, and legs; the face is usually not affected. Typically, it occurs in spring or early summer, and is triggered by several hours of sun exposure after a long period of no sun exposure. It's not just an unsightly rash though — this sun allergy may also itch or burn.

Generally, as the summer progresses, the sun can be tolerated without a rash appearing; however, PMLE tends to recur every year after the first episode. While there is no known prevention for that first rash of the season, wearing sun-protective clothing and sunscreens with a high SPF may help keep it at bay. But, if it's severe or persistent, you should seek medical treatment.

What if, after just a few minutes in the sun, you start to break out in hives? You may be suffering from solar urticaria. which can occur on any exposed skin - but similar to PMLE, it normally spares the face. Once you're out of the sun, it tends to disappear just as suddenly as it appeared, and rarely lasts longer than 24 hours.

You’re taking doxycycline for your acne, and notice that your skin turns red and burns more easily. This is known as a drug-induced photosensitivity, and can be caused by a number of medications, both oral and topical. The rash can look varied in different people, but a sunburn response is most common. It can affect any part of the skin exposed to the sun — including the face.

If you know that the medication you are taking can cause photosensitivity, it's important to minimise sun exposure and maximise sun protection (sunscreen, sun-protective clothing, and seek shade). If you work outdoors, and this is not possible, it's best to discuss alternative treatment options that may not have this adverse effect. If the reaction has already happened, then treatment consists of symptom relief (so if the reaction is a sunburn, then usual sunburn care is recommended).

Steroid creams can be helpful for some cases; systemic steroids are rarely required for severe cases.You’ve just spent the weekend sipping some margaritas poolside, and notice a redness and blistering on your skin. It’s likely “Lime Disease” (not to be confused with Lyme Disease). Lemons or limes are a regular summertime culprit. I often see people with rashes on their hands after using lemons to lighten their hair, or squirting a lime into their margarita while sitting on the beach or by the pool. This is also known as phytophotodermatitis (I refer to it as vacation rash). The condition often goes away on its own, once the offending agent is removed. Immediate use of cool compresses (similar to how you would treat a sunburn) may be helpful. But, under your doctor's care, you may opt for steroids provided the rash doesn't resolve on its own, or is severe.

Sometimes skin conditions, for example lupus or rosacea, are not caused by the sun, but may flare up or worsen with sun exposure; these are known as photoexacerbated dermatoses. If you notice that your skin condition gets worse after you’ve been in the sun, limit your time outside, and be diligent about wearing a heavy sunscreen. People with genetic photodermatoses, which is rather rare, are very sensitive to the sun. The skin burns easily and severely, and can experience outbreaks from existing rashes with any amount of sun exposure. Also, developing skin cancer is a big concern.

Finally, metabolic photodermatoses, which can also be genetic, are caused by defects in enzymes that are required for chemical reactions in the body. This results in an imbalance of a substance or chemical. The most common group of metabolic photodermatoses are the porphyrias. Depending on the type of porphyria, the nervous system (e.g., the brain), skin, and other organs may be affected. If it's the skin that is affected, sun sensitivity, along with blisters and scarring, are to be expected. It varies by the type of porphyria, but, it usually cannot be cured. Lifestyle changes - such as sun avoidance and stringent sun protection, and alcohol avoidance, can be helpful. If you feel that you are suffering from sun sensitivity that doesn't go away, see a dermatologist to discuss your concerns and possible treatments. Some rarer conditions may be more challenging to treat, but common conditions are often easily managed with good and consistent sun protection, and medical treatments with topical steroids.