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Antihistamine prescriptions online

Antihistamines are an anti-allergic medications used to treat various allergic symptoms.

Antihistamines can help treat allergic reactions with a consultation from one of our board-certified doctors online. You can now get a personalized prescription or refill an existing medicine facilitated by certified doctors with efficient and easy-to-use online services.

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Classification of Antihistamines

Antihistamines are broadly classified into H1 and H2 categories. H1 antihistamines are further subdivided into first and second-generation antihistamines based on anti-allergic activity and the receptors that they act on.

H-1 Antihistamines

  • First Generation: First-generation antihistamines impart sedative effects along with antihistaminic activity. These include drugs like Diphenhydramine, Chlorpheniramine, and Promethazine.
  • Second Generation: Second-generation antihistamines do not have sedating properties, and they include drugs like Cetirizine (Zyrtec), Levocetirizine (Xyzal), and Loratadine (Claritin).

H-2 Antihistamines

Examples of H-2 histamines include the following:

  • Cimetidine
  • Ranitidine
  • Famotidine

These antihistamines treat various conditions, including allergic reactions, allergic rhinitis, urticaria, and gastrointestinal conditions. The classification of antihistamines helps determine their clinical use, efficacy, and potential side effects.

Uses of Antihistamine

As the name suggests, antihistamines are used to reverse the action of histamine. Histamine is a mediator that causes allergic reactions, but it is also involved in other processes like the sleep and wake cycle, cognitive ability, and gastric acid secretion. Histamine is a substance produced by your cells as an immune response to allergy triggers.

It is present more abundantly in the lungs, skin, and gastrointestinal tract. Histamine also works as a neurotransmitter. Antihistamines work by counteracting the effects of histamine, leading to their antihistamine properties.

Antihistamines are used to treat allergy symptoms and severe conditions like anaphylactic shock. Allergy symptoms like hay fever, conjunctivitis, reaction to insect bites or stings. Antihistamines are sometimes also used for a short time treatment of insomnia. Antihistamines are also used to treat symptoms of motion sickness, for example, nausea and vomiting.

Side effects of anti-histamine

Side effects of anti-histamines include:

  • Drowsiness/Sedation
  • Cognitive impairment
  • Increased appetite
  • Dry mouth
  • Blurred vision
  • Difficulty peeing
  • Lightheadedness 
  • Nervousness
  • Fainting
  • Fast pounding heartbeat

How antihistamine works?

Histamine acts on H-receptors, which include H1, H2, H3, and H4. H1 and H4 receptors are involved in allergic reactions. Most allergies occur as repeated exposure to allergens, leading to dilation and increased permeability of blood vessels. Most antihistamines act on H1 receptors to block this pathway, producing their anti-allergic effect.

Histamine H1 receptors are found in the tuberomammillary nucleus of the brain, in smooth muscle, endothelium, and mast cells throughout the body. H1-antihistamines attach to these receptors. This binding reduces allergy symptoms by blocking histamine-induced swelling and vasodilation.

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Hi I’m Dr. Nicole. How may I help you?

Dr. Nicole, I have an allergic reaction to pollen and frequently sneeze. Could I receive the prescription for this condition, please?


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  • Cetirizine, 10mg, once daily.

Antihistamine risks

If you have hypertension, urinary retention, cardiovascular disease, and increased ocular pressure, you should use antihistamines with caution. It is also recommended to avoid the use of alcohol with antihistamines as they can increase the risk of drowsiness.

FAQs about antihistamine

What are Topical Antihistamines?

Topical antihistamines relieve pain and itching on the skin due to insect bites, burns, and minor cuts and resolve rashes caused by poison ivy, oak, or poisonous sumac.

What are three commonly used Antihistamines?

Cetirizine, Loratadine, and Diphenhydramine are the three most commonly used antihistamines. Cetrizine and Loratadine are non-drowsy antihistamines that are less likely to cause sedation or induce sleep and are used for allergies and hay fever. Diphenhydramine has sedative potential and is used for allergies, hay fever, and hives. It is also used as a sleep aid to relieve the symptoms of motion sickness.

Do Antihistamines raise blood pressure?

No, antihistamines do not generally increase blood pressure, but if you take medications for high blood pressure, taking antihistamines may increase blood pressure.

What are the prescription allergy medicines for adults?

Cetrizine, Fexofenadine, and Azelastine are commonly prescribed allergy medications for adults. Other medications like Beclomethasone, Flunisolide, and Fluticasone are some drugs that adults use to treat allergies. They are not antihistamine drugs they are corticosteroids with anti-inflammatory properties.

What are the common prescription allergy medicines for children?

Prescription medications for children include Azelastine, Desloratadine, and Hydroxyzine, as commonly prescribed antihistamines.

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