Reddish purple knee area, had hives. Advise?

Hi,

Thanks for your query.

Hives is a kind of allergic reaction that causes itchy weals with erythema, that settles with steroids and antiitching medicines.
Often the diagnosis is clinical and hence no investigations may be asked, The lesions are typical, pink with raised edges and central scaling, multiple and itchy, usually over exposed parts or all over body, there may be any history of allergy in past..
The tests you may need are allergen skin test, and if it is in families serum c1q esterase .
occasionally rash may not be hives, like say typical calf rash may be confused with purpura, in such cases a complete blood count may also be helpful.

I hope this answers your query.
Wishing you a rapid recovery.