Showing posts with label h2 receptor. Show all posts
Showing posts with label h2 receptor. Show all posts

Side effects of antihistamines

First-generation antihistamines


Common side effects of first-generation antihistamines include:


  • drowsiness

  • impaired thinking

  • dry mouth

  • dizziness

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.


Less common side effects of first-generation antihistamines include:


  • insomnia – difficulty sleeping

  • nightmares

  • hallucinations – seeing or hearing things that aren’t real

  • itchy skin

Rare side effects of first-generation antihistamines include:


Contact your GP if you experience these rare side effects.


Second-generation antihistamines


A few people will experience drowsiness after taking second-generation antihistamines. If you find yourself feeling drowsy, do not drive, drink alcohol or use tools or machines.


As well as drowsiness, other side effects of second-generation antihistamines include:


  • headache

  • dry mouth

  • dry nose

These side effects are usually short-lasting and should pass quickly.


Rarer side effects include:


  • rapid heartbeat

  • chest tightness

Contact your GP if you have these rare side effects.


H2 receptor antagonists


Antihistamines that are used to treat stomach ulcers are known as H2 receptor antagonists. Side effects of this type of antihistamine are uncommon but may include:


  • diarrhoea

  • headache

  • dizziness

  • skin rashes

  • tiredness

Antihistamines:Antihistamine medicine counteracts the action of histamine (a chemical released during an allergic reaction). For example, loratadine, hydroxyzine.
Drowsiness:Drowsiness is when someone feels extremely tired and uncontrollably near to sleep.
Fever:A high temperature, also known as a fever, is when someone’s body temperature goes above the normal 37°C (98.6°F).
Heart:The heart is a muscular organ that pumps blood around the body.



Side effects of antihistamines

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What antihistamines are used for

Antihistamines are mainly used to help control symptoms of health conditions associated with allergic reactions.


Although antihistamines can’t cure these types of conditions because they don’t affect the underlying cause, they can often provide considerable symptom relief.


Conditions that can benefit from the use of antihistamines include:


  • hay fever

  • allergic rhinitis – inflammation of the nasal passages

  • atopic eczema – a common allergic skin condition

  • urticaria – also known as nettle rash and hives

  • allergic conjunctivitis – inflammation of the eyes

  • allergic reactions that are caused by insect bites or insect stings

  • mild allergic reactions that are caused by food allergies; more serious allergic reactions (anaphylaxis) usually require treatment with adrenaline (a chemical that can reverse many of the processes associated with an allergic reaction)

Other uses


As well as being used to treat allergic conditions, antihistamines also have a number of other uses, including treating stomach ulcers (sores that develop on the lining of the stomach) and insomnia (problems falling asleep).


Stomach ulcers


A type of antihistamine, known as a H2-receptor antagonist, is sometimes used to treat stomach ulcers. This is because histamine can also stimulate the production of stomach acid.


H2-receptor antagonists can be used to block the ‘acid-stimulating’ effect of histamine, which helps to reduce the acid level in the stomach and digestive system.


Read more about treating stomach ulcers for more information.


Insomnia


First-generation antihistamines may be of some benefit in the short-term treatment of insomnia, particularly if the symptoms of sleeplessness are caused by an underlying allergic condition, such as an allergic skin condition.


The long-term use of antihistamines to treat insomnia is not recommended because there are more effective treatments. In addition, there’s a risk that you could become addicted to the sedating effects of first-generation antihistamines.


Read more about treating insomnia for more information.


Adrenaline:Adrenaline is a hormone produced at times of stress that affects heart rate, blood circulation and other functions of the body.
Allergic:An allergen is a substance that reacts with the body’s immune system and causes an allergic reaction.
Anaphylactic shock:Anaphylactic shock is a severe and sometimes life-threatening allergic reaction, causing swelling of body tissues and a drop in blood pressure.
Anxiety:Anxiety is an unpleasant feeling when you feel worried, uneasy or distressed about something that may or may not be about to happen.
Chronic:Chronic usually means a condition that continues for a long time or keeps coming back.
Congestion:Congestion is an excess of fluid in part of the body, often causing a blockage.
Decongestant:Decongestant medicine relieves congestion by reducing the swelling of the lining the nose and sinuses and drying up the mucous.
Drowsiness:Drowsiness is when someone feels extremely tired and uncontrollably near to sleep.
Fever:A high temperature, also known as a fever, is when someone’s body temperature goes above the normal 37°C (98.6°F).
Morning sickness:Morning sickness refers to the nausea and vomiting experienced early in a pregnancy, not necessarily in the morning.
Sickness:Vomiting is when you bring up the contents of your stomach through your mouth.
Sneezing:Sneezing is an involuntary expulsion of air and bacteria from the nose and mouth.
Stomach:The sac-like organ of the digestive system. It helps digest food by churning it and mixing it with acids to break it down into smaller pieces.
Swelling:Inflammation is the body’s response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Ulcers:An ulcer is a sore break in the skin, or on the inside lining of the body.



What antihistamines are used for

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