Allegra and Claritin are both second generation antihistamines with a low risk of sedation; however, Allegra has the lowest risk of sedation out of all antihistamines so is preferred if an antihistamine is needed for people working in safety-critical jobs.

Other differences:

• Studies point to Claritin being more effective than Allegra for allergic rhinitis (faster onset of action, more symptom relief)
• Allegra may provide more eye symptom relief.
• Studies suggest Allegra may be more effective than Claritin for wheal and flare reactions (an allergic skin reaction).
• Allegra should not be taken with grapefruit juice. Claritin has no reported food interactions.

Allegra is a brand name for the drug fexofenadine and Claritin is a brand name for the drug loratadine. Both fexofenadine and loratadine are popular antihistamines with many similarities but there are some important differences.

Which is more sedating? Allegra or Claritin?

Allegra (fexofenadine) and Claritin (loratadine) are second-generation antihistamines. Second-generation antihistamines were first developed in the 1990s to provide allergy relief without the unwanted side effect of sedation common to first-generation antihistamines such as promethazine and diphenhydramine.

Fexofenadine (Allegra), even in dosages exceeding those recommended, is the least sedating of all second-generation antihistamines, so is considered the antihistamine of choice for people in safety-critical jobs such as airline pilots. Loratadine (Claritin) is unlikely to cause CNS side effects such as sedation, or confusion when used at recommended dosages of 10mg/day; however, side effects may be more likely when used at higher dosages.

Which is more effective for Allergic rhinitis?

Trials have shown both Allegra (fexofenadine) and Claritin (loratadine) are significantly more effective than placebo (a pretend pill) for reducing symptoms associated with allergic rhinitis, hay fever, and other allergies. Trials have not consistently shown that one antihistamine is more effective than another; however, one trial reported loratadine had a quicker onset of action and provided more symptom relief in 836 patients with allergic rhinitis (Harold 2001). This result backed up a previous trial conducted in 2000 (Prenner et al).

Another trial reported fexofenadine as superior to loratadine at reducing ocular symptoms of rhinitis but similar to loratadine at reducing other rhinitis symptoms (Innes).

Intranasal or ophthalmic (into the eye) antihistamines have a quicker onset of action than oral antihistamines (within about 15 minutes); however, they need to be administered several times daily. In people with allergic rhinoconjunctivitis and predominantly eye symptoms, ophthalmic antihistamines work much quicker (within 3 to 15 minutes) and are much more effective than any other form of treatment. Intranasal antihistamines are as effective as intranasal cromolyn, intranasal nedocromil, and leukotriene modifiers in seasonal allergic rhinitis; however, are not as effective at relieving nasal congestion and other symptoms as intranasal glucocorticoids.

For urticaria and other skin reactions

All second generation antihistamines, including Allegra and Claritin, are effective for acute and chronic urticaria, although more trials have been conducted in people with chronic urticaria. No trial has consistently found one antihistamine to be better than another.

One trial reported that fexofenadine was superior to loratadine with regards to wheal and flare suppression (allergic skin reaction), with a faster onset of effect and a more effective suppression of the flare at each time point in the study (Kaliner et al).

For Postnasal Drip

Post nasal drip may occur for various reasons - allergies (particularly to dairy), colds or flu, various drugs (including birth control pills and high blood pressure tablets), cold temperatures, bright lights, hormonal changes and spicy foods.

Thin postnasal drip secretions caused by allergies may be treated with antihistamines. Second-generation antihistamines such as Allegra and Claritin may offer better relief than older-type antihistamines such as promethazine (older antihistamines tend to thicken post-nasal secretions). Intranasal antihistamines, such as azelastine, have a faster onset of action (15 minutes) and appear more effective than oral antihistamines although require more frequent administration. Other treatments include decongestants, cromolyn, and corticosteroid nasal sprays.

In the treatment of post nasal drip caused by nonallergic causes, oral second-generation antihistamines are not very effective. However, the intranasal antihistamine azelastine is effective. Azelastine improves all rhinitis symptoms including nasal congestion, postnasal drip, sneezing and sleeping difficulty. The most common side effect is a metallic aftertaste; however, this is more likely at higher dosages and tends to dissipate with continued use.

If thin nasal mucus secretions become thick and turn yellow or green, bacterial infection is likely and a doctor should be seen to obtain antibiotics.

To Relieve Cold Symptoms

Second-generation antihistamines (such as Allegra and Claritin) have limited effectiveness at relieving symptoms of cold such as a runny nose and sneezing (only 45% of adults felt better after using them compared to 35% with placebo [a pretend pill]). Effects were only noticeable if used within the first two days of a cold, use of antihistamines made no difference thereafter.

Administration

The antihistamine effects of Allegra and Claritin last for at least 24 hours, therefore, they are both given once daily. Fexofenadine, the active ingredient of Allegra works within two hours. Claritin may not reach its peak effect for two to three hours since most of its antihistamine activity is attributable to its active metabolite desloratadine, which loratadine is metabolized to in the liver.

Side Effects, Interactions and Price

Side effects are generally mild with second-generation antihistamines and include a headache and rarely dry mouth, and nausea. Both Allegra and Claritin appear free from adverse cardiovascular effects. Few major interactions have been reported with either Allegra or Claritin; however, there is the possibility that side effects such as sedation, confusion, and mental alertness may be enhanced if Claritin is given with other drugs with this side effect.

Grapefruit juice appears to decrease the rate and extent of absorption of fexofenadine by about 30%. Loratadine has no reported interactions with grapefruit or grapefruit products. More studies are needed to determine if there are any interactions between second generation antihistamines and herbal products and other types of food. Always speak with your doctor of pharmacist before using any drugs in combination.

Cost is similar for 30 Allegra and 30 Claritin tablets and both are available as generics.

See also: Drugs.com Compare Tool - Allegra vs Claritin