Summer is a great time - it's warm, the evenings are longer, the smell of freshly cut grass. What's not so wonderful is the puffy eyes, the runny nose and the constant sneezing because of hay fever. If this affects you, you're probably all too familiar with antihistamines.

But what exactly do antihistamines do? Are there any side effects? Let's find out:

How do antihistamines work?

Histamine is a protein that the immune system uses to protect the body from infection. If your immune system detects a a 'foreign object', it will send histamines to the nearby cells.

This causes the blood vessels to expand and the surrounding skin to swell.

The HSE says: "The release of histamine causes the process of inflammation to begin and leads to nearby tissue becoming red and swollen. It can also affect the nerves in the skin, making the skin feel itchy."

In the case of hay fever, pollen is the harmless foreign object that your body sees as a major threat.

Types of antihistamines

There are two types of antihistamines:

  • First-generation antihistamines: These can cause drowsiness in people
  • Second-generation antihistamines: These do not usually cause drowsiness

Second-generation antihistamines are generally more popular than first-generation ones because of the drowsiness caused by first-generation anithistamines.

Where can I get them?

Most antihistamines are available over the counter in any pharmacy without prescription, but always read the label before taking any medication.

Who can take them?

The following conditions can be worsened or aggravated by antihistamines, according to the HSE:

  • Asthma
  • Diabetes
  • High blood pressure
  • Epilepsy
  • Glaucoma
  • An enlarged prostate gland
  • Heart disease
  • Liver disease
  • Kidney disease
  • Bladder stones or obstructions
  • Overactive thyroid
  • Stomach or intestinal blockages

As a general rule, it's best that pregnant woman don't take medication unless there is a clinical need. If you feel like you need antihistamines, visit your GP. The same applies if you're breastfeeding.

Always read the label or consult your GP when giving your child medication. Most antihistamines are not suitable for children under two.

Are there any side effects?

First-generation antihistamines cause drowsiness, impaired thinking, dry mouth and dizziness.

The HSE points out: "It's important not to underestimate the effects of antihistamine-related drowsiness. Some first-generation antihistamines can impair abilities such as co-ordination, reaction times and judgment in the same way that alcohol consumption can.

"Therefore it's very important that you do not drive or use power tools or heavy machinery after taking a first-generation antihistamine."

Second-generation antihistamines can cause headaches, dry mouth and dry nose.

If you think you need antihistamines for an allergy. consult your GP before taking any medication.

Download the RSVPLive App


