Taking Benadryl With Allegra

In most cases, it would not be recommended to take Benadryl (diphenhydramine) and Allegra (fexofenadine) together.

Since they are both antihistamines, taking both would be considered a 'therapeutic duplication' and you likely won't get much additional benefit from adding one to the other.

Nevertheless, there are some exceptions to using Allegra with Benadryl, and this is discussed in the next sections.

Taking Two Antihistamines

Both Benadryl & Allegra are classified as antihistamines and have the same mechanism of action.

We separate the two drugs within their class by generation (e.g. first-generation antihistamine, second-generation antihistamine) to differentiate specific attributes they possess, such as duration of action and whether or not they cause sedation.

First-generation antihistamines, like Benadryl, are known for their short duration of action (typically around 4 to 6 hours) and their sedative effects.

Second-generation antihistamines, like Allegra, last longer (around 24 hours) and have less pronounced sedative effects. In fact, many are considered essentially 'non-drowsy'.

Regardless of their specific classification, they work the same way by blocking the histamine-1 receptor in our bodies.

This prevents histamine from binding to it and producing the allergy symptoms we are all familiar with (sneezing, runny nose, watery eyes, etc...).

As Benadryl and Allegra are in the same class of medications, and work in the same way, concurrent use is not recommended, or very often, needed.

Typically, you would not expect the combination of the two drugs to work any better for your allergy symptoms versus one alone.

Additionally, the use of two antihistamines at the same time could increase the risk of side effects associated with them, including:

• Sedation
• Dizziness
• Dry mouth
• Dry eyes
• Constipation

When Is Use Together Okay?

While you wouldn't want to use Benadryl and Allegra at the same time to treat allergy symptoms, there are some instances in which using both Benadryl and Allegra is warranted.

First off, most people intend to use Benadryl as a sedative to help sleep.

Taking it alongside Allegra for this purpose would typically be considered OK if used only on an intermittent basis. Be aware though that you may experience some additive side effects such as dry mouth and dry eyes.

Secondly, Benadryl has been shown in some studies to be a more effective medication for the treatment of anaphylactic reactions versus other antihistamines.

Anaphylactic reactions (e.g. bee stings, peanuts, etc...) can be extremely serious and often must be treated right away.

In addition to seeking medical attention, Benadryl is often recommended to be used as soon as possible to help reduce inflammation (although second-generation antihistamines can be used, and may be preferred in some cases due to their lack of sedative effects).

If you take Allegra on a regular basis for your seasonal allergies and were in a situation where you were having a serious allergic reaction, Benadryl would most likely be an appropriate choice to use before seeking medical attention.