ir ‧ ri ‧ tant /ˈɪrətənt, ˈɪrɪtənt/ BrE AmE noun [countable]
1 . formal something that keeps annoying you over a period of time:
Low-flying aircraft are a constant irritant in this area.
2 . a substance that can make a part of your body painful and sore:
a skin irritant