What are the different types of allergies?

There are several types of allergic reactions. One of the most well-known is anaphylactic allergy, or type I, which can be life-threatening. Another type is delayed allergy, or type 4, which can appear some time after exposure. It is usually not as dangerous, but it is still recommended to avoid the allergen in the future. It can be difficult to determine the exact cause of an allergy without thorough testing done under the supervision of an allergist. That's why it's usually best to consult a doctor if an allergy is suspected.