Antihistamines are used to block the effects of histamine, a protein that helps fight against infection. In general, Histamine is useful until you have an allergy.

When a harmless substance (e.g. pollen) is detected as a threat by histamins in your body, you will have allergy reaction such as sneeze, running nose, itchy eyes. To prevent this happen, it might be good to block the histamines.

Herbs like nettle tea, green tea, chamomile tea are natural antihistamines because they can prevent the secretion of histamines.You can also buy antihistamine tablets from shops as they do not need prescription.