Is there an allergic synovitis?

Nine patients had attacks of joint pain and sometimes swelling precipitated by certain foods or associated with allergic manifestations. All were atopic subjects--three having strong evidence of Type I (immediate) allergy and three 'urticarial arthralgia', in which attacks of severe urticaria and joint pain occurred coincidentally. Food allergy appeared to be responsible for the joint symptoms in three patients and in one it was possible to precipitate swelling of a knee due to synovitis with effusion by drinking milk a few hours beforehand, the synovial fluid having mildly inflammatory features and a relatively high eosinophil count. It seems that allergy is an occasional cause of episodic rheumatic pain or synovitis in certain atopic patients, whether or not they have an underlying arthritis. These are usually Type I hypersensitivity reactions, though it is thought that some food-allergic reactions are immune complex-mediated.