One of the first treatment avenues for a runny and itchy nose, or any other light to mild allergic reaction is likely to be over the counter medicine. Most patients tend to consider taking antihistamines. However, it’s essential to be mindful of the different types of antihistamines to select the most effective treatment.

Antihistamines work by blocking histamine, which affects the cells in your body. If your body detects something harmful, such as an infection, it will release histamine to fight it off. The histamine causes blood vessels to expand and the airway to swell (known as inflammation), which is supposed to help protect your body against what it perceives as dangerous.

However, people with allergies tend to experience the opposite. This is because their bodies confuse harmless matter, like pollen or dust, as harmful. As a result, their bodies produce histamine, which leads their allergic reactions.

By taking antihistamines, you can counter the effect of your body’s histamine production. It’s an effective way to reduce or even eliminate your allergic reaction. In the pharmaceutical industry, there are two types of antihistamines: First generation, and second-generation antihistamines.

First-generation antihistamines

These antihistamines have multiple side effects, but the most important side-effect is drowsiness. You might believe that the sedating qualities of the medication will lead to a good night’s sleep, when, in fact, it disrupts the natural sleep pattern.

If you were to take a first-generation antihistamine for conditions like allergic rhinitis, you’d be very likely to wake up the next morning feeling like you’ve got a fog-headed hangover.

You might even be taking a first-generation antihistamine without knowing it: It often forms part of cough syrups, flu medication as well as “sinus” medication. Despite their well-known and published side effects of drowsiness that has led to vehicle and plane accidents, these medications are still readily available over the counter.

Second-generation antihistamines

Second-generation antihistamines combat all the adverse side effects of the first-generation antihistamines.

The newer second-generation antihistamines have two categories – those that do not cross into the brain at all, like fexofenadine, which does not cause drowsiness. Others, like Fexofenadine, Cetirizine and Desloratadine, have a limited cross over into the brain but do not have a significant impact on your motor functioning. Fexofenadine does not cross the blood brain barrier and is non-sedating. Loratadine  is regarded as non-sedating, with cetirizine classified as less-sedating.

Antihistamines might not be so great for children and the elderly 

How our bodies process and get rid of these medications is very important – especially in the elderly, who tend to have liver and renal impairment. These patients need a reduced dose because the medication gets altered by our livers and excreted by our kidneys.

Fexofenadine is the only molecule that is removed from the body without being processed, which means no change to dosing.

Children and babies are always more vulnerable to the adverse effects of medication. The best way to make sure we keep them safe is always to make sure if the medication is registered for their age group.

Of the second-generation antihistamines, fexofenadine is registered from six months of age, so it’s safe to administer to babies of six months and older if they are suffering from skin allergies or hives.

In conclusion

Choosing an effective antihistamine is easy when you prioritise:

  1. Safety
  2. Efficacy

Once you have the correct medication, stay the course with consistent administration. And it’s always best to ask your pharmacist or doctor for advice if you’re not sure about either of these points. 

  • The purpose of this article is to raise awareness of allergies and the treatment options that are available for it. This article should by no means be used, or viewed, as a primary source for medical or other professional advice – please arrange for a personal consultation with your medical practitioner before taking any decisions that could affect the wellbeing of you or your loved ones. Read our medical disclaimer for more information.

Marinda McDonald

Dr Marinda McDonald has offered specialised treatments for allergies for most of her professional career. Read more about her on the home page of this website (

1 Comment

It’s sneezing season! | The Allergy Clinic · October 15, 2019 at 9:24 am

[…] Allergic rhinitis happens when you breathe in foreign matter or particles – originating from sources like cats, dogs, pollen and mould. Once it’s in your system, your body mistakenly recognises these particles as harmful bacteria or parasites. In an attempt to protect your body against these particles, your immune system will launch an attack to drive them out. It does this by producing histamine (read more about histamines, and antihistamines, here). […]

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