Dermatology Questions? Ask an Online Dermatologist.
Dear Customer, Welcome to just answer.The cause of the red itchy rash could be due to urticaria,could be due to irritation of the skin due to the cloth of the trousers,Vasculitis due to irritation of the blood vessels due to exercising excessively,fungal infections and folliculitis, atopic dermatitis as also idiopathic.
The purpuric rash may be secondary to a drug allergy if you are on any medicines for any disease,or antibiotics taken recently.Autoimmune diseases may also be considered,a Dermatological consultation may be sought if the rash persists.Use of non-sedating antihistaminics like Fexofenadine(Allegra)/Claritidin(Loratidine) or Cetrizine may be tried with bedtime sedating antihistaminics like benadryl/Atarax.
A soothing lotion or a mild steroid cream may help if the rash is non-ineffective in nature.