Diphenhydramine starts working within 30 minutes and reaches its peak within one to two hours of being taken.

But, if you want it to do its best work, it’s smart to take diphenhydramine preventatively before you experience any allergy symptoms at all. When taken ahead of exposure to your allergens, it can work proactively and prevent the release of histamine in response to allergens in the first place.

Antihistamine or steroid nasal sprays can complement diphenhydramine and help reduce your symptoms. Additionally, antihistamine eye drops can relieve those itchy, watery eyes that you can’t stop rubbing.

If you’re still struggling, you might be dealing with a cold rather than allergies. Talk to your doctor or healthcare professional to figure out your best next steps.

No matter how desperate you are to reduce your allergy symptoms, avoid doubling up on doses or taking a dose sooner than is recommended. Doing so can be dangerous. You also shouldn’t mix different antihistamines without a physician's guidance.

Diphenhydramine may cause constipation, diarrhea, drowsiness, or headache. For more, please see additional important safety information at https://picnicallergy.com/drug-facts/diphenhydramine.