Cetirizine marketed as Zyrtec, Reactine .

Cetirizine is an antihistamine that blocks the action of histamine and reduces the symptoms of an allergic reaction.

Chlorphenamine or Chlorpheniramine marketed as CPM, Chlor-Trimeton, Piriton, Chlor-Tripolon.

This medicine contains the active ingredient chlorphenamine maleate which belongs to a group of medicines called sedating antihistamines. Chlorphenamine acts by blocking the binding of histamine to receptors in the body, preventing or relieving the typical symptoms of an allergic reaction. Chlorphenamine has antidepressant properties that inhibits reuptake of the neurotransmitter serotonin.

Cinnarizine marketed as Stugeron, Stunarone.

Cinnarizine belongs to a group called antihistamines. Cinnarizine works by blocking the receptors in the vomiting center to prevent the brain from sending nerve messages to the stomach thereby prevents vomiting.

Loratadine marketed as Claritin, Claritin-D, Claritine, Clarityn, Clarityne, Fristamin, Lorfast, Lomilan, Flonidan, Symphoral, Roletra, Rinolan, AllergyX, Alavert, Tidilor, Claritin-D, Clarinase.

Loratadine is a long acting antihistamine. This drug blocks one type of receptor for histamine which helps to lessen allergic reaction. This drug does not enter the brain from the blood therefore it does not cause drowsiness.