Instruct: Given a question, retrieve relevant documents that can help answer the question.
Query: What does antihistamine treat?
Antihistamines are drugs which treat allergic rhinitis and other allergies.[1] Antihistamines can give relief when a person has nasal congestion, sneezing, or hives because of pollen, dust mites, or animal allergy.[1] Typically people take antihistamines as an inexpensive, generic, over-the-counter drug with few side effects.[1] As an alternative to taking an antihistamine, people who suffer from allergies can instead avoid the substance which irritates them. However, this is not always possible as some substances, such as pollen, are carried in the air, thus making allergic reactions caused by them generally unavoidable.[1] Antihistamines are usually for short-term treatment.[1] Chronic allergies increase the risk of health problems which antihistamines might not treat, including asthma, sinusitis, and lower respiratory tract infection.[1] Doctors recommend that people talk to them before any longer term use of antihistamines.[1]
H2-antihistamines are among first-line therapy to treat gastrointestinal conditions including peptic ulcers and gastroesophageal reflux disease. Some formulations are available over the counter. Most side effects are due to cross-reactivity with unintended receptors. Cimetidine, for example, is notorious for antagonizing androgenic testosterone and DHT receptors at high doses.
Setastine (Loderix) is an antihistamine used to treat allergies and rhinitis.
Antihistamines, which are commonly used to treat allergy symptoms, interfere with skin tests, as they can prevent the skin from reacting to the allergens being tested. People who take an antihistamine need either to choose a different form of allergy test or to stop taking the antihistimine temporarily before the test. The period of time needed can range from a day or two to 10 days or longer, depending on the specific medication. Some medications not primarily used as antihistamines, including tricyclic antidepressants,
phenothiazine-based antipsychotics, and several kinds of medications used for gastrointestinal disorders, can similarly interfere with skin tests.
Antihistamines such as diphenhydramine and chlorpheniramine are commonly used as treatment. People treated with H1 antihistamines exhibit reduced production of histamine and leukotrienes as well as downregulation of adhesion molecule expression on the vasculature which in turn attenuates allergic symptoms by 40–50%.
Not much published research exists which compares the efficacy and safety of the various antihistamines available.[1] The research which does exist are mostly short term studies or studies which look at too few people to make general assumptions.[1] Another gap in the research is in information reporting the health effects for individuals with long term allergies to take antihistamines for a long period of time.[1] Newer antihistamines have been demonstrated to be effective in treating hives.[1] However, there is not research comparing the relative efficacy of these drugs.[1]
Levocetirizine is called a non-sedating antihistamine as it does not enter the brain in significant amounts, and is therefore unlikely to cause drowsiness. Cardiac safety with repolarization may be better than some other antihistamines, as levocetirizine does not significantly prolong the QT Interval in healthy individuals. However, some people may still experience some slight sleepiness, headache, mouth dryness, lightheadedness, vision problems (mainly blurred vision), palpitations and fatigue.
Chlorcyclizine (Di-Paralene, Mantadil, Pruresidine, Trihistan) is a first-generation antihistamine of the diphenylmethylpiperazine group marketed in the United States and certain other countries. It is used primarily to treat allergy symptoms such as rhinitis, urticaria, and pruritus, and may also be used as an antiemetic. In addition to its antihistamine effects, chlorcyclizine also has some anticholinergic, antiserotonergic, and local anesthetic properties. It also has been studied as a potential treatment for hepatitis C.
Propiomazine (Largon, Propavan, Indorm, Serentin, Dorevane, Dorevan) is an antihistamine blocking H1 receptors. It is used to treat insomnia, and to produce sleepiness or drowsiness and to relieve anxiety before or during surgery or other procedures and in combination with analgetics also during labor. Propiomazine is a phenothiazine, but is not used as a neuroleptic because it does not block dopamine receptors well.
In traditional medicine, fruits have been used to treat leprosy, fever, asthma, bronchitis, and jaundice. The fruit possesses mast cell-stabilizing, antianaphylactic, and antihistaminic potential. In Bangladesh, the roots are used to treat osteoarthritis and joint pain. A paste made of leaves is applied to the skin to treat scabies.
Non-sedating antihistamines that block the histamine H1 receptors are the first line of therapy. First generation antihistamines such as diphenhydramine or hydroxyzine block both central and peripheral H1 receptors and can be sedating. Second generation antihistamines such as loratadine, cetirizine, or desloratadine selectively antagonize the peripheral H1 receptors and are less sedating, less anticholinergic, and generally preferred over the first generation antihistamines.
People who don’t respond to the maximum dose of H1 antihistamines may benefit from increasing the dose, then to switching to another non-sedating antihistamine, then to adding a leukotriene antagonist, then to using an older antihistamine, then to using systemic steroids and finally to using ciclosporin or omalizumab.
State-dependent retrieval is demonstrated when material learned under one State is best recalled in that same state. A study by Carter and Cassady (1998) showed this effect with antihistamine. In other words, if you study while on hay fever tablets, then you will recall more of what you studied if you test yourself while on antihistamines in comparison to testing yourself while not on antihistamines after having studied on antihistamines.
Extrahepatic cholestasis can usually be treated by surgery.
Pruritis in cholestatic jaundice is treated by antihistamines, ursodeoxycholic acid, and phenobarbital.
Nalfurafine hydrochloride can also treat pruritus caused by chronic liver disease and was recently approved in Japan for this purpose.
Epinastine (brand names Alesion, Elestat, Purivist, Relestat) is a second-generation antihistamine and mast cell stabilizer that is used in eye drops to treat allergic conjunctivitis. It is produced by Allergan and marketed by Inspire in the United States. It is highly selective for the H receptor and does not cross the blood-brain-barrier.
It is also used to treat people 12 years and above with chronic spontaneous urticaria (also called chronic idiopathic urticaria), which cannot be treated with elevated doses of H1-antihistamines.
Capsaicin-induced asthma might be treated with oral antihistamines or corticosteroids.
The vast majority of marketed H1-antihistamines are receptor antagonists and only a minority of marketed compounds are inverse agonists at the receptor.[2][5] Clinically, H1-antihistamines are used to treat allergic reactions and mast cell-related disorders. Sedation is a common side effect of H1-antihistamines that readily cross the blood–brain barrier; some of these drugs, such as diphenhydramine and doxylamine, are therefore used to treat insomnia. H1-antihistamines can also reduce inflammation, since the expression of NF-κB, the transcription factor the regulates inflammatory processes, is promoted by both the receptor's constitutive activity and agonist (i.e., histamine) binding at the H1 receptor.[2]
Currently most people who use an antihistamine to treat allergies use a second generation drug.[1]
Immunotherapy is used to treat allergies. While allergy treatments (such as antihistamines or corticosteroids) treat allergic symptoms, immunotherapy can reduce sensitivity to allergens, lessening its severity.
Pheniramine (INN, trade name Avil, among others) is an antihistamine with anticholinergic properties used to treat allergic conditions such as hay fever or urticaria. It has relatively strong sedative effects, and may sometimes be used off-label as an over-the-counter sleeping pill in a similar manner to other sedating antihistamines such as diphenhydramine. Pheniramine is also commonly found in eyedrops used for the treatment of allergic conjunctivitis.
Nasal congestion may affect the sinus openings and the eustachian tubes and may lead to difficulty or inability to clear the ears.
To prevent congestion, allergies can be treated by the use of antihistamines, decongestants and nasal sprays, and allergy desensitization. Recently developed antihistamines do not cross the blood-brain barrier and do not produce drowsiness, but may only be available by prescription.
First aid for fire ant stings includes external treatments and oral medicines. There are also many home remedies of varying efficacy, including immediate application of a solution of half bleach and half water, or aloe vera gel – the latter of which is also often included in over-the-counter creams that also include medically tested and verified treatments.[7] External, topical treatments include the anesthetic benzocaine, the antihistamine diphenhydramine, and the corticosteroid hydrocortisone.[7] Antihistamines or topical corticosteroids may help reduce the itching and will generally benefit local sting reactions.[36] Oral medicine include antihistamines.[37] Severe allergic reactions to fire ant stings, including severe chest pain, nausea, severe sweating, loss of breath, serious swelling, and slurred speech,[38] can be fatal if not treated.[39]
Antihistamines can alleviate some of the milder symptoms of an allergic reaction, but do not treat all symptoms of anaphylaxis. Antihistamines block the action of histamine, which causes blood vessels to dilate and become leaky to plasma proteins. Histamine also causes itchiness by acting on sensory nerve terminals. The most common antihistamine given for food allergies is diphenhydramine.
This can be due to:Treatment of an allergic transfusion reaction is to immediately stop the transfusion. If the only symptoms are mild (i.e., hives and itching), the patient may be treated with an antihistamine and if the symptoms completely disappear and the patient feels well, the transfusion may be restarted. A mild transfusion reaction during infusion usually does not progress to a more severe anaphlyactic reaction after infusion of additional product from the same unit. If the symptoms are more than mild, the transfusion should not be restarted.
Most studies of antihistamines reported on people who are younger, so the effects on people over age 65 are not as well understood.[1] Older people are more likely to experience drowsiness from antihistamine use than younger people.[1] Also, most of the research has been on white people and other ethnicities are not as represented in the research.[1] The evidence does not report how antihistamines affect women differently than men.[1] Different studies have reported on antihistamine use in children, with various studies finding evidence that certain antihistamines could be used by children 2 years of age, and other drugs being safer for younger or older children.[1]