Antihistamines (commonly referred to as hay fever tablets) are a group of medications that prevent the level of histamine from rising in our body and reduce the symptoms this can cause. Antihistamines can be used to treat a range of conditions including mild allergic reactions, motion sickness and insomnia. However, the term "antihistamines" most commonly refers to medications that are used to treat hay fever.
There’s an array of antihistamine products available, so let our resident pharmacist take you through where to start and how to choose between them.
If you are suffering from hay fever or allergic-type symptoms such as an itchy nose, itchy rash or bite on the skin or redness and minor swelling of the skin, then an antihistamine may help relieve these symptoms for you.
Mild allergic reactions to products (washing detergent, creams, perfume), food or plant reactions (stinging nettles) can be safely treated with over-the-counter antihistamines and should get better in hours to days. Make sure to avoid whatever caused the reaction in future.
If you find that you are getting regular allergic reactions and do not know the reason why, you should discuss with your doctor, and you may benefit from getting allergy testing.
Histamine is a naturally occurring chemical in your body that is activated and released from your cells when your immune system is triggered by a foreign substance. Histamine sets off a chain reaction, allowing your immune system to detect and remove the thing that caused it.
Whilst a useful and important response, the release of histamine causes redness, swelling and itchiness that can be bothersome. Individuals that suffer from hay fever or show allergic sensitivity to harmless stimuli have a higher than normal amount of histamine released by the immune system.
Hay fever medications help to prevent and reduce the effect of histamine in the body, and therefore are effective at relieving allergic symptoms. However, not all antihistamines are the same
Older antihistamines are more likely to cause drowsiness – this may be an advantage if symptoms are worse at night, but not if you need to operate heavy machinery or drive long distances.
They work for a shorter amount of time, typically 4 to 6 hours, so you might need to take them several times a day or just when the pollen count is higher, typically early mornings and evenings.
Despite this, some people think they work better for their particular hay fever – it's a question of trial and error what works for you.
They are similar in effectiveness, but you may find one works better than the other. Both get to work within 1 to 3 hours, cetirizine perhaps slightly faster, and both peak in effectiveness after 8 to 12 hours, but last for at least 24 hours – loratadine possibly longer.
At this dose, they are unlikely to make you drowsy. The newer antihistamines include fexofenadine which works in a similar way to the other non-drowsy antihistamines, but offers more effective relief.
The best time to take antihistamines can depend on the specific type of antihistamine and your symptoms. Many people take them in the evening to avoid drowsiness during the day. However, some non-sedating antihistamines can be taken in the morning. Taking antihistamines before the expected onset of symptoms, such as before exposure to allergens, can be a proactive approach for some individuals.
This is often recommended in cases where you know you'll be exposed to allergens that trigger your symptoms. It's called preemptive or prophylactic use. Different medications have different doses and schedules for how often you can take them. Check with your pharmacist or read the box carefully if you are not sure.
Most antihistamines are safe to take for long periods of time, for example throughout hay fever season, however chlorphenamine should not be used for longer than two weeks at a time without consulting a doctor. Antihistamine creams are also available to buy and may be more suitable for treating localised reactions such as insect bites.
Talk to your doctor if you are pregnant or breastfeeding before taking antihistamines. Do not take any antihistamines three days before taking an allergy skin test as this can affect your results.
Like all medications, don’t take them if you have previously had an allergic reaction to the medication, if you have severe <u>kidney</u> or <u>liver</u> problems, or if you have other medications or medical conditions that you would normally discuss with your doctor or pharmacist before starting something new.
Like all medicines, antihistamines can cause side effects. The specific side effects depend on whether the antihistamine causes drowsiness or not.
Side Effects of Drowsy Antihistamines:
It is advised not to drive or use machinery after taking these antihistamines.
Side Effects of Non-Drowsy Antihistamines:
Check the accompanying leaflet for a comprehensive list of possible side effects and guidance on when to seek medical help.
Interactions with Other Medications:
Before taking antihistamines with other medicines, consult a pharmacist or GP. Some medications may not mix well, affecting their effectiveness or increasing the risk of side effects. Examples of medicines that could pose problems include certain:
Additionally, exercise caution when consuming alcohol with antihistamines, especially those that induce drowsiness, as it can heighten the sedative effects. While food and most drinks typically do not affect antihistamines, it's advisable to review the medicine leaflet for confirmation.
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