Diphenhydramine is not the answer during allergic reactions

Editor’s Note: In Healio Allergy/Asthma’s column, “Food Allergy: Fact vs. Fiction,” Douglas H. Jones, MD, breaks down what’s true and what’s myth for a variety of topics related to food allergies. If you have a question you would like answered in this column, email Jones at rmaaimd@gmail.com or Richard Gawel at rgawel@healio.com.

I often get asked about Benadryl or its generic counterpart, diphenhydramine. A vast majority of the time when people have a rash or think they are having an allergic reaction, their knee-jerk response is to reach for the diphenhydramine.

Even when people with allergies are already taking cetirizine or fexofenadine and they have breakthrough symptoms, Benadryl is their treatment answer.

I surveyed emergency room doctors and asked what made them give diphenhydramine vs. another nonsedating antihistamine, and they largely provided two answers:

1. The belief that it worked faster and better

2. Cost, as it is cheaper

I then asked if they had any data to support the idea that it worked “faster and better,” and none of them could provide any. The reason they could not give any is because I do not believe it exists, as I have yet to see it.

Why do we continue to reach for it? Largely because of myth. But what does the data say?

I published a paper and looked at how quickly diphenhydramine (both oral and intramuscular injection) suppressed histamine in a skin test as compared with oral fexofenadine.

The bottom line is that there was no statistically significant difference. Oral fexofenadine performed just as well as even an injection of diphenhydramine. The only difference was fexofenadine lasted longer!

Four myths of diphenhydramine

1. It works faster than other non-sedating antihistamines.

2. It works better than other non-sedating antihistamines.

3. It should be used in more severe allergic reactions.

4. It should be used in food allergies.

Four facts of diphenhydramine

1. It can impair measures of driving performance more than alcohol in experimental conditions.

2. It increases risk of injury at work more than hypnotics or narcotics.

3. Impairment is independent of feeling tired.

4. Diphenhydramine should never replace the use of epinephrine in an acute and severe allergic reaction.

Epinephrine is the answer

The take-home message is that in a severe, acute allergic reaction, epinephrine is the drug of choice. Most fatalities arise with food allergy when there is a delay in epinephrine being given or it is not administered at all.

Many people fear epinephrine, but the medication is not the problem. It is the remedy. The problem is that a severe allergic reaction is already occurring — and often quickly.

Many people will delay administering epinephrine or not administer it at all because of the stigma of going to the emergency room. In a severe reaction, that will likely be happening anyway. Giving epinephrine early in anaphylaxis can prevent furthering complications or catastrophe.

Reference:

• Jones DH, et al. Ann Allergy Asthma Immunol. 2008;doi:10.1016/S1081-1206(10)60470-X.

For more information:

Douglas H. Jones, MD, FAAAAI, FACAAI, is cofounder of Global Food Therapy, Food Allergy Support Team and OITConnect, the director at Rocky Mountain Allergy at Tanner Clinic, and a Healio Allergy/Asthma Peer Perspective Board Member. He can be reached at rmaaimd@gmail.com or on Instagram @drdouglasjones.