Sun hives, or photodermatitis, occur when the skin has an abnormal reaction to sunlight. Several factors can cause sun hives, including an allergic reaction to sunlight, diseases such as lupus or medications that cause photosensitivity, such as St. John’s Wort. In addition to the hives, you may also experience an intense, burning itch, as well as chills, headache and a fever. You may experience these symptoms while you are in the sunlight or several minutes to hours after exposure.
Apply an over-the-counter hydrocortisone cream, as well as an antihistamine cream such as diphenhydramine, to the hives. The hydrocortisone reduces inflammation, and the antihistamine relieves itching.
Take an oral allergy medicine, such as cetirizine, fexofenadine or loratidine. You can also take diphenhydramine instead of using a topical antihistamine cream. To prevent an overdose, do not use oral diphenhydramine and diphenhydramine cream together, and make sure to follow all package directions regarding dosage.
Dip a clean washcloth in cold water, wring the cloth until damp and apply it to the hives. The cool moisture can help to reduce the swelling and itching.