There isn't necessarily a "best" non-drowsy antihistamine, as individuals often have varying effects to different antihistamines.
Nevertheless, when it comes to the treatment of seasonal allergies, your best bet is most likely a choice between the second and third-generation antihistamines, most of which are "non-drowsy".
Second-generation antihistamines include:
- Claritin/Alavert (loratadine)
- Allegra (fexofenadine)
- Zyrtec (cetirizine)
- Clarinex (desloratadine)
Third -generation antihistamines include:
- Xyzal (levocetirizine)
Of the above medications, all are non-drowsy except Zyrtec and Xyzal. However, those two are not nearly as sedating as first-generation antihistamines such as Benadryl and Chlor-Trimeton. In addition, even "non-drowsy" antihistamines can cause sedation and drowsiness in a low percentage of users.
The duration of action of "non-drowsy" antihistamines is generally 24 hours with the peak effect occurring eight to twelve hours after taking the dose. While none of these second/third-generation antihistamines are considered head and shoulders better than another there are some differences to consider.
Comparing Non-Drowsy Antihistamines
Allegra (fexofenadine), Zyrtec (cetirizine), and Claritin (loratidine) are available as generics unlike Xyzal. Clarinex, while available generically, is prescription only.
Of the available generics, Claritin (loratadine) is generally the lowest cost over the counter options so is a great first option to try.
Although overall effectiveness of each of the second generation antihistamines is very similar, studies have shown that Zyrtec and Xyzal tend to have better and stronger effects for longer periods of time. However, as mentioned above, Zyrtec and Xyzal are not considered non-drowsy.
Studies have not shown significant differences between the three true "non-drowsy" antihistamines, Allegra, Claritin and Clarinex. If you are choosing between these, try Claritin first as it is generally the least expensive.
Every individual is different and may respond differently to each medication. This makes good old-fashioned trial and error an option if you're not getting the desired effect from one of these antihistamines.