When it comes to treating allergies, antihistamines are undoubtedly the most commonly used medications with amazing success rates and exceptional results. While completely curing allergies is, as of now, still impossible – although in some instances, immunotherapies have proven to be moderately successful – antihistamines can be used to successfully prevent an allergic reaction or treat the symptoms during a flare-up.

What’s on this page?

While allergy symptoms tend to remain mild and pass rather quickly on their own in a significant percentage of cases, more severe allergies will require additional treatment in order not to adversely affect one’s quality of life. People struggling with these kinds of allergies should consult with their doctor about the available treatment options. In many cases, medicines classified as antihistamines will be prescribed. They are very efficient at tackling the symptoms of seasonal allergies such as hay fever or allergic rhinitis, but also of allergic reactions to pet dander, dust mites and insect bites.

Antihistamines currently available on the market can be obtained in varied degrees of strength, meaning that not all of them are prescription-only – the milder ones can be bought over the counter, while the stronger medicines will require you to obtain a prescription from a certified medical professional.

What exactly is an allergic reaction?

An allergic reaction occurs when the body’s immune system misidentifies certain harmless substances (allergens) as threat, similar to infections. When this occurs, the body will begin releasing a number of chemicals, most notably, histamine.

Within the body, histamine plays a number of different roles. This naturally synthesised compound is produced in the mast cells and is considered to be an integral part of the body’s immune system. The mast cells responsible for histamine production are located in numerous parts of the body, so the release of the chemical is most likely to occur in that area where the contact with an allergen also occurred. Most commonly, this includes the respiratory tract and the skin.

Reaction to perceived incidents

The immune system is constantly ‘on the lookout’ for potential problems such as skin damage or introduction of harmful substances to the system. Once an incident is detected, histamine is released only to bind to a type of cells known as H1 receptors. In normal circumstances, this process allows for a quick distribution of chemicals and cells to heal the area and fight off the infection. However, in case of an allergic reaction, there is no real threat to be fought and instead the overreaction will begin causing problems, causing the allegedly affected body part to swell, becoming red and itchy.

Antihistamines mechanism of action

Antihistamines block this process by inhibiting the activity of H1 receptors, so even though histamine will be present within the system, it won’t be able to reach the target area nor bind to H1 receptors, thus reducing the symptoms of an allergic reaction or completely preventing them from occurring.

In some situations, antihistamines can also be highly adept at tackling nausea and vomiting, especially so in cases of motion sickness. While this mechanism of action isn’t fully understood as of now, there are some indications that they interfere with H1 receptors in the brain that are tasked with controlling the urge to vomit.

Which antihistamines can I buy in the UK?

Antihistamines are commonly classified into two distinct categories, usually called first and second generation antihistamines. The first generation encompasses the older medications that are known to cause considerable side effects, most notably the intense drowsiness. The more recent developments in the medicine allowed the pharmaceutical companies to overcome this seatback and develop so-called second and third generation antihistamines that don’t cause this sometimes problematic side effect.

How are antihistamines administered?

Antihistamines can be obtained in a variety of different forms and can thus be administered in a number of different ways. Most commonly, you will encounter antihistamines in the following forms:

  • Eye drops
  • Nasal sprays
  • Tablets
  • Capsules
  • Creams
  • Lotions

Of course, each of the mentioned forms has its own pros and cons, being more suitable to treat certain symptoms than the others. The final choice is most likely to be made by your doctor or pharmacist who will help you choose the most suitable option, depending on the exact nature of your condition and the triggers you commonly react to.