Allergic reactions in anesthesia are a rare event, however, might be life threatening when occurred. Clinical manifestations may not be indicative at first, and difficult to differentiate from different situations during operation and anesthesia. Colloids represent a group of fluids often used during perioperative period that, among other adverse reactions, have an allergic potential. Albumin is a natural colloid that has the lowest incidence of these reactions. However, it is found as an additional substance in other blood products, and, therefore, has to be taken into consideration if anaphylaxis occurs. Dextrans cause the most severe reactions due to dextran reactive antibodies. Pretreatment with Dextran 1 may inhibit the reaction. Gelatins have the highest incidence of anaphylaxis among colloids. Patients with history of allergy to some food, vaccines, cosmetics containing gelatin are at greater perioperative risk for anaphylaxis. Not to forget, gelatins are also a part of topical haemostatic agents used in surgery. Testing for colloid allergies is limited due to their pathophysiologic mechanism, so the clinical assessment is usually essential. Treatment of anaphylaxis caused by colloids is the same as for any other cause. This is a review of the most common colloids and their association with allergic reactions in everyday practice.