How long does Benadryl take to work?
Benadryl is quickly absorbed after oral administration and it starts to work within 30 minutes with peak effects reached within one to two hours. The effects of Benadryl last from four to six hours. Benadryl in the injectable form has a rapid onset of action. You will know when Benadryl starts to work because your allergy symptoms, such as congestion, runny nose, itchy eyes, or a skin rash, will start to feel better.
References
- Benadryl Injection [Package Insert]. Revised 04/2021. Parke-Davis. https://www.drugs.com/pro/benadryl-injection.html
- U.S. National Library of Medicine MedlinePlus. Antihistamines for allergies. Available at: https://medlineplus.gov/ency/patientinstructions/000549.htm.
Read next
What is the Benadryl hat man?
The Hat Man is a fictional figure that started appearing on certain internet sites in the early 2000s that has recently been referred to as the “Benadryl Hat Man” after reports of people hallucinating and sighting him after overconsumption or abuse of Benadryl. Most of these reports have appeared on Reddit or the image-based bulletin site 4chan. Continue reading
What is the max dose of diphenhydramine for adults?
The maximum oral dose of diphenhydramine for adults is generally reported as 100mg for a single dose or no more than 300mg in 24 hours, but this can vary depending on what condition diphenhydramine is being used for, the salt of diphenhydramine used (there are two salts available in the US diphenhydramine citrate and diphenhydramine chloride), the age of the person, how much diphenhydramine they have tolerated before, and if they are on any interacting medications. Taking too much diphenhydramine can be fatal. Continue reading
Which antihistamines are safe for dogs?
According to the American Kennel Club (AKC), you can give the antihistamine Benadryl (diphenhydramine) to your dog, but you should always check with your vet first. Continue reading
Related medical questions
- How much Benadryl can I take? What is too much?
- What are the effects of taking expired benadryl?
- Does Benadryl make you sleepy?
- Does Benadryl help with or cause anxiety?
- How much Benadryl can I give my dog?
- What can I give my dog for motion sickness?
- Can you take Benadryl while pregnant?
- What is the dosage amount of children's Benadryl to give a 4 year old child who weighs 30 lbs?
- How do you choose the right allergy medication?
- Poison Ivy
- What should you keep in your medicine cabinet for kids?
- Emergency Treatment Plans for Allergic Reactions in Children
Drug information
- Benadryl Information for Consumers
- Benadryl prescribing info & package insert (for Health Professionals)
- Side Effects of Benadryl (detailed)
- Benadryl user reviews (78)
Related support groups
- Benadryl (111 questions, 167 members)
- Allergic Reactions (224 questions, 468 members)
- Nausea/Vomiting (444 questions, 925 members)
- Pruritus (186 questions, 322 members)
- Cough (171 questions, 456 members)
- Hives (83 questions, 213 members)
- Cold Symptoms (46 questions, 44 members)
- Allergic Rhinitis (43 questions, 92 members)
- Hay Fever (36 questions, 55 members)
- Urticaria (33 questions, 72 members)
- Motion Sickness (21 questions, 31 members)