Hello, Thank you for posting on HCM. The condition you have referred to is called Urticaria or hives. Its an allergic manifestation of skin, where an allergen leads to release of certain substances from your blood, leading to itchy skin rash and swelling over soft tissues. Its proper management requires thorough history, clinical and laboratory work-up.You may have to go for specific tests like patch test, food prick test, IgE antibody levels etc. As for treatment part, best would be the avoidance of allergen as far as possible. I think in your case its due to co-trimoxazole tablets . Consult a dermatologist for the proper management. I would also advise you a short course of various anti-histaminics with or without oral corticosteroids. For non- responding cases there are many other drugs like dapsone, cyclosporine, montelukast, omalizumab etc which can be used in certain selected cases. Hope this will help you in resolving your query. Thank you Dr Hardik Pitroda