Hives and Joint Pain

My sister had a case of hives show up on her legs and then move to her arms and then all over her body two days ago.  She took Benadryll and the hives have seemed to subside, however, she now is feeling bad joint pain all over her body.  Any idea what this may be?  She has not tried any new food or drink, nor has she been on any antibiotic.

Thanks!

[Dr. Kokil Mathur]

Hi
Thanks for writing to the forum!
Well, joint pains with rash can be seen in SLE, psoriatic arthritis, fibromyalgia, polymayalgia rheumatica and chronic fatigue syndrome. Gout, though typically affects the great toe, can cause multiple joint pain with rash. Hashimotos Thyroiditis is another possibility. Hayfever and rheumatoid arthritis too should also be ruled out.
Another possibility is reactive arthritis, which could have occurred in reaction to something—in this case rash. In this case you need to rule out the cause for the hives or urticaria. Urticaria is usually triggered by allergens, such as drugs, foods, insect bites, inhaled substances, in response to sunlight, cold, heat, stress, exercise, or a viral infection. Other common allergens are pollen, mold, dust, pet dander, or cosmetics. You may need to consult an allergy specialist.
Hope this helps. Do discuss these possibilities with your doctor and get your sister examined. Please let me know if there is any thing else and do keep me posted. Take care!