Solar urticaria (SU) is a rare condition in which exposure to ultraviolet or UV radiation, or sometimes even visible light, induces a case of urticaria or hives that can appear in both covered and uncovered areas of the skin. It is classified as a type of physical urticaria. The classification of disease types is somewhat controversial. One classification system distinguished various types of SU based on the wavelength of the radiation that causes the breakout; another classification system is based on the type of allergen that initiates a breakout.
When exposed to light, the skin cells of someone with solar urticaria release potent chemicals (including histamine), causing their blood vessels to open and fluid to collect within the skin.
Their skin feels itchy and has red patches, which may be swollen.
These may look like weals or a nettle rash, and can take up to an hour to appear after exposure to light, then coming on quickly and settling within a similar period. There is no permanent change to the skin.
What causes solar urticaria?
The cause of solar urticaria is not clearly defined but may be due to an antigen-antibody reaction. It seems that a chemical created in the body (photoallergen) reacts with UV radiation to cause an allergic reaction that manifests as urticaria.
Who gets solar urticaria?
Solar urticaria is rare. It can occur in both males and females at any time of life. The mean age of onset is 35 years, but it has occurred in infant children through to those aged 70 years.
Is solar urticaria serious?
If a large enough area of the body is affected, the loss of fluid into the skin may result in light-headedness, pallor and nausea. It’s important if you have this complaint to avoid developing a state of shock by limiting the affected areas.
Symptoms of solar urticaria
Following limited exposure to sunlight, sufferers may develop an itchy or burning redness on exposed skin. Initial presentation has also been reported after first solarium use.
Symptoms usually develop within five minutes of sun/UV exposure and often develop from an unpleasant sensation to itching, redness and swelling, followed by localized or widespread development of wheals (an urticarial flare). Gradual resolution then follows over 1-2 hours.
Rarely, a more prolonged exposure may be required for symptoms to develop, or the onset of symptoms may be delayed for several hours. With extensive whealing some patients also experience headache, nausea, bronchospasm (asthma-type respiratory symptoms) and syncope (dizziness) which may become life threatening (although this is rare). Conversely, in some people with mild disease, or in those who quickly recognize their onset and avoid further exposure, whealing may not be reported.
Sun-exposed areas are most commonly affected, although occasionally reactions are seen in dermal areas that are not exposed to the sun. Rarely sun-exposed sites are spared suggesting that tolerance may occur.
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Solar Urticaria Treatments
Solar urticaria can be uncomfortable, but there are treatments you can perform at home to reduce the redness and itching. Cool water will help to soothe your irritated skin. Applying cold compresses takes the heat out of the rash, as does a cool soak in the bathtub. Over-the-counter medications, such as antihistamines, can provide even more relief. Ibuprofen, used as directed, can ease the soreness, and anti-itch or hydrocortisone cream can significantly reduce the itching. Before using any over-the-counter medications, be sure to ask your doctor or pharmacist about possible interactions with any prescription medications that you take. Overall, the best thing you can do to treat solar urticaria is to stay out of the sun.
A severe case of solar urticaria requires treatment by a doctor. When home remedies and over-the-counter treatments don’t work, your doctor might prescribe a prescription-strength antihistamine and a steroid-based cream [source: Harvard Medical School]. In extreme cases, the doctor will require additional tests and prescribe a treatment that is right for you.