Antihistamines are drugs commonly used to treat autoimmune conditions such as allergies. Histamine is a naturally produced chemical in the body by the immune system. When a body misinterprets the environmental particles as allergens, it creates excess histamine resulting in allergies such as rash, itchiness, or hives.
To treat such autoimmune conditions, steroids and allergy shots are used. However, antihistamines are the prioritized medications to treat allergic reactions such as hives, urticaria, runny nose, conjunctivitis, swelling, itchy or watery eyes, and hay fever. They can also treat motion sickness, nausea, vomiting, anxiety, insomnia (short-term treatment), and Parkinson’s disease.
Types of Antihistamines
Several types of antihistamines are present to treat a number of diseases. Two major types are as follows:
- H-1 Blockers or H-1 receptor antagonists
- H-2 Blockers or H-2 receptor antagonists
H-1 Blockers or H-1 receptor antagonists
H-1 blockers are further divided into two categories. These are first-generation and second-generation H-1 blockers.
First-generation and Second generation:
The difference between first-generation antihistamines and second-generation histamine is as follows:
- First-generation antihistamine causes drowsiness by crossing the blood-brain barrier and stimulating sleep.
- On the contrary, the second generation doesn’t cross the brain barrier and doesn’t cause drowsiness.
- Both generations treat allergies such as rhinitis, hay fever, conjunctivitis, hives, food allergies, insect bites, stings, and colds.
- However, first-generation also treats insomnia, anxiety, and motion sickness.
H-2 Blockers or H-2 receptor antagonists
- It treats allergies and GI conditions such as gastritis, nausea, vomiting, and gastric ulcers.
- H-2 Blockers can also treat heartburn and Zollinger-Ellison syndrome.
In which form are Antihistamines available?
Antihistamines are over-the-counter and prescribed medication to treat allergies. These are available in tablets, capsules, gels, eyedrops, liquid, and nasal sprays.
Types of Over-the-counter antihistamines:
These includes
Antihistamines that are only available with a prescription are as follows:
- Hydroxyzine (Atarax, Vistaril)
- Desloratadine (Clarinex)
- Eyedrops Azelastine (Optivar)
- Nasal Sprays Azelastine (Astelin, Astepro)
Common Side Effects of Antihistamine
Common side effects of antihistamines vary according to the type and generation of the drug.
Side effects of the first generation of H-1 Blockers
The common side effects include:
- Drowsiness
- Low energy or stamina due to drowsiness
- Dry mouth and eyes
- Dizziness
- Headache
- Convulsions/ Seizures
- Tachycardia
- Double or Blurred vision
- Constipation
- Urinary retention
- Low Blood Pressure
- Tremors (in rare cases)
Side effects of the second generation of H-1 Blockers
The common side effects include:
- Headache
- Fatigue
- Cough
- Convulsions/ Seizures (rare)
- Sore throat
- Weight gain (Obesity)
- Nausea and Vomiting
- Abdominal pain
- Agitation (rare)
- Bloating (rare)
Side effects of H-2 blockers
The common side effects of H-2 blockers include:
- Drowsiness
- Fatigue
- Headache
- Muscular pain
- Moodiness in Children
- Joint pain
- Confusion
- Dizziness
- Swelling and tenderness of breast
Rare Side effects of Antihistamines
- Bruising
- Unusual bleeding
- Pale skin and eyes
- Swelling of the face and lower limbs
- Tightness in chest
- Loss of appetite
- Nightmares
- Ringing or buzzing in the ears
- Dryness of nose
- Pounding of heart
FAQs
- What are the rare side effects of antihistamines?
- What are antihistamines, and why are they used?
- What are the common side effects of antihistamines?
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