What Are Non-Drowsy Antihistamines? How They Work?

Your immune system reacts to harmful foreign substances to eliminate them from the body. Sometimes, your immune system may react to bee venom, pollen, pet dander, or another foreign substance that usually does not cause any reaction in most people. This is when you experience allergy symptoms, such as sneezing, itchy eyes, wheezing, nasal congestion, and rash. The most common treatment option includes taking antihistamines to slow down immune system and reduce severity of different symptoms. Unfortunately, most antihistamine medicines can cause drowsiness, but you can also find some antihistamines that won't make you drowsy. Keep reading to learn more.

Types of Non Drowsy Antihistamines

Sometimes, it becomes difficult to deal with your allergy symptoms, and that is when you decide to take antihistamines to feel better. There are basically two types of antihistamines – first generation antihistamines and second generation antihistamines. First generation antihistamines can have different side effects, and drowsiness is one of them. But that is not the case with second-generation antihistamines. Here are some main types of medications:

Names of Drugs


Acrivastine (Benadryl, Pregnancy category B)


Loratadine (Claritin, Pregnancy category B)

Not as potent as Allegra or Zyrtec, but is sedating only at higher doses

Levocetirizine (Xyzal, Pregnancy category B)


Mizolastine (Mizollen)

Non-sedating, but should be avoided in pregnancy

Cetirizine (Zyrtec, Pregnancy category B)

Quite sedating at normal doses

Fexofenadine (Allegra, Pregnancy category C)

Least sedating – does not cause serious drowsiness even with higher doses

Desloratadine (Clarinex,Pregnancy category C)


Azelastine (Astelin, Pregnancy category C)

May cause sedation

While non drowsy antihistamines work great, they are not for everyone. Here is more about age restrictions when it comes to taking these antihistamines orally.

  • Age 6 months or older can take antihistamines like cetirizine, desloratadine, and fexofenadine.
  • Age 2 years and older can take antihistamines like loratadine.
  • Age 12 years and older can take antihistamines like levocetirizine.

Note: You should never underestimate the drowsiness caused by first-generation antihistamines. In some cases, the effect continues into the next day of taking an antihistamine. Second-generation non-sedating antihistamines are still relatively new drugs with larger molecules and less lipiphilic. While they are less likely to break the blood-brain barrier and cause drowsiness, you should still avoid driving or performing skilled tasks after taking them because there is no 100% guarantee.

How Do Antihistamines Work?

Allergy happens when your body is exposed to triggers, be it ragweed, pollen, dust mites or pet dander. In this case, your body produces histamines to fight against these substances. Although histamine is actually a useful substance and helps clear infection, it is important to block its effects in case of allergic reactions. Histamines give you stuffy and swelling nose, runny nose and eyes, itchy nose and mouth and even rash on the skin (hives).

Antihistamines work by blocking or reducing histamines to soothe lots of allergic symptoms from seasonal allergy, indoor allergy and food allergy. But this is not a cure-all drug. You may need a decongestant to treat nose congestion or take other medications combining antihistamine and decongestant to get relief. Antihistamines are usually quite potent and start working within half an hour of taking a tablet – they are at their peak within 1-2 hours.

How to Use Antihistamines

You will find most non drowsy antihistamines in pill form – they are usually available in tablets or sometimes as capsules filled with liquid. A dissolving pill is also available for people who trouble swallowing pills. But these antihistamines are also available in liquid form. It means you can find it in flavored syrup form if you do not want to swallow large pills, which makes it safe for children.

When to Call Your Doctor

It is a good idea to call your doctor if you suspect your symptoms are due to an allergic reaction. Also, talk to your doctor if an allergic reaction occurs soon after starting a new medication. Call the local emergency number or 911 if a severe allergic reaction develops. Besides, it is important to give yourself an epinephrine shot right away if you are carrying an epinephrine auto-injector.

Precautions and Side Effects of Taking Antihistamines

While antihistamines, like non drowsy antihistamines, work great to block the effects of histamine, you should avoid taking them if you have a metabolic disorder called acute porphyria. It is also a good idea to avoid them if you have kidney or liver problems or are pregnant. Avoid first-generation antihistamines if you are suffering from prostate enlargement.

You usually do not experience serious side effects if you take antihistamines to treat allergy. If side effects do happens, the most common ones may include agitation, dizziness, headache, drowsiness, dry mouth, blurred vision, stomach upset, and difficulty passing urine.

Keep in mind that some other medicines can also react with antihistamines and cause certain complications. They may react with antifungal medicines and antidepressants. Also, avoid alcohol when you are taking antihistamine because it can make your drowsiness worse. Talk to your doctor if you experience serious side effects.

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