What are antihistamines and how do they work?

Antihistamines are medicines that block a natural chemical in the body called histamine. Histamine is released by the immune system during allergic reactions and causes symptoms like sneezing, itchy eyes, and a runny nose. By blocking histamine from attaching to its receptors on cells, antihistamines reduce or prevent these symptoms.

Key points:

  • Antihistamines mainly target H1 receptors to ease allergy symptoms such as hay fever and skin rashes.
  • Some types block H2 receptors to lower stomach acid production.
  • They come in older types that can cause drowsiness and newer types that are less likely to do so.
  • Antihistamines may also help with nausea, motion sickness, and certain stomach issues.

This text has been fact-checked for accuracy by medino's clinical team.