How do antihistamines cause allergies?

Antihistamines are used as remedy for allergies. It is often regarded as a cold treatment and may be less effective. Allergies can be mild, for instance hay fever; sometimes they can also be life threatening, such as a bee or nut allergy that results in anaphylactic shock and if not treated immediately may also lead to death. Antihistamine causes your body to create and release histamines, which will cause symptoms like sneezing, itchiness, coughing. The above reaction will not occur initially when you are exposed to allergen. This develops an antigen that is responsible for creating allergic reaction. Antihistamines stop these histamines from their function by attaching to the receptor before the histamine can, thereby preventing allergic reaction. Antihistamine does not cure the allergies but they can stop the allergic reaction from becoming severe or life-threatening. Antihistamines can help control the itching, swelling and also, skin rashes. With proper controlled intake of antihistamine, allergies can be a nuisance but cannot be fatal. Antihistamines do have a few side effects. Antihistamines are available of two types, i.e. older and newer. The old Antihistamines cause drowsiness or sedate you. Now, antihistamines work only on nasal receptors, so drowsiness is not a concern.