Antihistamines are a type of medicine often used to treat a number of allergic health conditions.These include:hay feverallergic rhinitis – inflammation of the nose due to an allergic reaction to substances such as dust mitesallergic skin conditions, such as eczema or urticaria (hives)allergic conjunctivitis – inflammation of the eyesFor more information about the conditions that this type of medicine can help treat, see Antihistamines – what it is used for.Antihistamines work by blocking the effects of a protein called histamine (see below). They’re available in tablet or capsule form (oral antihistamines), creams, lotions and gels (topical antihistamines) and as a nasal spray.How antihistamines workHistamine is a protein that the immune system uses to help protect the body’s cells against infection. The immune system is the body’s natural defence against illness and infection.If the immune system detects a harmful foreign object, such as bacteria or a virus, it will release histamine into nearby cells. The histamine causes small blood vessels to expand and the surrounding skin to swell. This is known as inflammation.The expansion of the blood vessels allows an increased number of infection-fighting white blood cells to be sent to the site of the infection. The swelling of the surrounding skin also makes it harder for an infection to spread to other parts of the body.Histamine is usually a useful protein, but if you’re having an allergic reaction it’s sometimes necessary to block its effects. Allergic reactions occur when your immune system mistakes a harmless substance, such as pollen, as a threat.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.Types of antihistamineThere are a number of antihistamine medicines, which are classified in two groups. These are:first-generation antihistamines, which cause symptoms of drowsiness in most people; they include diphenhydramine and chlorphenaminesecond-generation antihistamines, which do not usually causes symptoms of drowsiness and include loratadine and cetirizineSecond-generation antihistamines are usually recommended. Do not underestimate the levels of drowsiness caused by first-generation antihistamines – their effects can continue into the next day if you only take them at night.Research has found that adults who regularly take first-generation antihistamines are more likely to be involved in serious accidents. Similarly, children who regularly take first-generation antihistamines perform less well at school than would usually be expected.An exception to these recommendations is sometimes made if the drowsiness caused by first-generation antihistamines can be of some use. For example, if you’re having problems sleeping because you have itchy skin.Where do I get them?Many antihistamines are available direct from your pharmacist without prescription.SafetyEven though antihistamines are a non-prescription medication, you shouldn’t assume that they’re safe for everyone to take.It’s also important to only take antihistamines as directed. Overdoses are possible and overuse can lead to addiction.Before taking antihistamines, always read the patient information leaflet that comes with the medicine.For more information see Antihistamines – who can use it.Allergen:An allergen is a substance that reacts with the body’s immune system and causes an allergic reaction.Allergic:An allergen is a substance that reacts with the body’s immune system and causes an allergic reaction.Blood:Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.Blood vessels:Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.Drowsiness:Drowsiness is when someone feels extremely tired and uncontrollably near to sleep.Fever:A fever is when you have a high body temperature (over 38°C or 100.4°F).Heart:The heart is a muscular organ that pumps blood around the body.Immune system:The immune system is the body’s defence system, which helps protect it from disease, bacteria and viruses.Sneezing:Sneezing is an involuntary expulsion of air and bacteria from the nose and mouth.Vomiting is when you bring up the contents of your stomach through your 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. Google+ Overview of Antihistamines
These include:
For more information about the conditions that this type of medicine can help treat, see Antihistamines – what it is used for.
Antihistamines work by blocking the effects of a protein called histamine (see below). They’re available in tablet or capsule form (oral antihistamines), creams, lotions and gels (topical antihistamines) and as a nasal spray.
How antihistamines work
Histamine is a protein that the immune system uses to help protect the body’s cells against infection. The immune system is the body’s natural defence against illness and infection.
If the immune system detects a harmful foreign object, such as bacteria or a virus, it will release histamine into nearby cells. The histamine causes small blood vessels to expand and the surrounding skin to swell. This is known as inflammation.
The expansion of the blood vessels allows an increased number of infection-fighting white blood cells to be sent to the site of the infection. The swelling of the surrounding skin also makes it harder for an infection to spread to other parts of the body.
Histamine is usually a useful protein, but if you’re having an allergic reaction it’s sometimes necessary to block its effects. Allergic reactions occur when your immune system mistakes a harmless substance, such as pollen, as a threat.
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.
Types of antihistamine
There are a number of antihistamine medicines, which are classified in two groups. These are:
Second-generation antihistamines are usually recommended. Do not underestimate the levels of drowsiness caused by first-generation antihistamines – their effects can continue into the next day if you only take them at night.
Research has found that adults who regularly take first-generation antihistamines are more likely to be involved in serious accidents. Similarly, children who regularly take first-generation antihistamines perform less well at school than would usually be expected.
An exception to these recommendations is sometimes made if the drowsiness caused by first-generation antihistamines can be of some use. For example, if you’re having problems sleeping because you have itchy skin.
Where do I get them?
Many antihistamines are available direct from your pharmacist without prescription.
Safety
Even though antihistamines are a non-prescription medication, you shouldn’t assume that they’re safe for everyone to take.
It’s also important to only take antihistamines as directed. Overdoses are possible and overuse can lead to addiction.
Before taking antihistamines, always read the patient information leaflet that comes with the medicine.
For more information see Antihistamines – who can use it.
Allergen:An allergen is a substance that reacts with the body’s immune system and causes an allergic reaction.Allergic:An allergen is a substance that reacts with the body’s immune system and causes an allergic reaction.Blood:Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.Blood vessels:Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.Drowsiness:Drowsiness is when someone feels extremely tired and uncontrollably near to sleep.Fever:A fever is when you have a high body temperature (over 38°C or 100.4°F).Heart:The heart is a muscular organ that pumps blood around the body.Immune system:The immune system is the body’s defence system, which helps protect it from disease, bacteria and viruses.Sneezing:Sneezing is an involuntary expulsion of air and bacteria from the nose and mouth.Vomiting is when you bring up the contents of your stomach through your 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.
