The least effective time to apply an antiperspirant is in the morning right after a shower. Deodorant gets into your sweat ducts and clogs them. However, since your sweat level in the morning is usually higher, your antiperspirant just washes off.

The best thing to do is apply it right before bed when your skin is drier and your sweat glands are not that active. Deodorant usually lasts 24 hours, which means your pores will be plugged even after you shower in the morning.