Is Hydroxyzine Effective for the Treatment of Allergies?

First Generation Antihistamine Hydroxyzine - Benefits and Side Effects

Mixed race woman blowing her nose
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Hydroxyzine is a first-generation, sedating antihistamine, which means it has similar side effects to Benadryl. It is marketed under the brand names Atarax and Vistaril but is also available in generic form. Hydroxyzine was originally developed as a sedative during the 1950’s but was found to have significant antihistamine properties.

Hydroxyzine for Allergies

Hydroxyzine is commonly prescribed for the treatment of various allergic conditions, particularly hives, but is also commonly used to treat itching, anxiety, insomnia, as well as nausea and vomiting.

The dose of hydroxyzine depends on the condition being treated, although a common dose is 25 to 50 milligrams every six hours. Hydroxyzine is also used for children, although the dose is calculated based on a child’s weight. However, the effects of sedation and drowsiness may lead instead to a prescription for one of the second-generation antihistamines such as Xyzal (levocetirizine.)

How Hydroxyzine Works for Allergies

Hydroxyzine works by blocking the H1 receptor, binding to them and decreasing the activity of histamine. Histamine allows more fluid to escape from the capillaries into the tissues, and it is this fluid you experience as a runny nose and watery eyes when you have an allergic reaction. Histamine also induces swelling and the production of wheels in rashes.

By blocking the H1 receptor, hydroxyzine is effective against these allergy symptoms. This can also help when itching (pruritis) is caused by allergies.

But hydroxyzine also crosses into the brain where it has further effects to cause drowsiness and sedation. These effects may not be wanted when treating allergies.

Second-Generation Antihistamines Derived from Hydroxyzine

The active metabolite of hydroxyzine is cetirizine (Zyrtec), which is available over-the-counter as a low-sedating antihistamine.

The active isomer of cetirizine is levocetirizine (Xyzal), which is available only by prescription and has become available in generic form. It doesn't cross into the brain as readily as hydroxyzine, and therefore it doesn't produce the same sedation It also does not produce the anti-anxiety effects of hydroxyzine for the same reason.

Zyrtec and Xyzal are better for the treatment of allergic rhinitis than hydroxyzine since they have fewer side effects and a longer duration of action. They are also effective for the treatment of hives and itching.

Zyrtec and Xyzal are not effective for the treatment of anxiety, insomnia or nausea, and vomiting, conditions for which hydroxyzine or other first generation antihistamines may be prescribed. (Despite hydroxyzine being a 50-year-old medication, it still has benefit for the treatment of various medical conditions.)

A review of studies of Xyzal (levocetirizine) in 2009 found that 5 mg/d was effective in reducing symptoms of seasonal allergic rhinitis (hayfever,) perennial allergic rhinitis, and chronic idiopathic urticaria (chronic hives of unknown cause, improving the quality of life, with an acceptable tolerability profile.

Bottom Line on Second Generation vs First-Generation Antihistamines

An advantage of the second-generation antihistamines (Zyrtec and Xyzal) is the lack of unwanted side effects such as sedation, drowsiness, and difficulty in concentrating and learning.

These side effects are of special concern when school-aged children are treated for long periods with hydroxyzine.

Xyzal (levocetirizine) is the only antihistamine with which there are no clinically relevant adverse effects on physical and psychomotor development in children aged six months to 12 years, according to studies.

That said, hydroxyzine continues to have non-allergy uses for the treatment of mild anxiety, insomnia, and nausea and vomiting. It may also be an inexpensive short-term medication for adults with allergies when the side effects of sedation may be beneficial (such as with insomnia or anxiety.)

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