Allergy is a common disorder among people and animals. When it comes to dealing with allergies, the first type of remedy that comes to mind is antihistamines, which could be a natural antihistamine found in some types of foods or commercial antihistamines.

Antihistamines are medication that inhibits the function of histamines in the body by blocking the histamine receptors. Symptoms of an allergy are normally triggered by histamines. By blocking the histamine receptors, different types of allergic reactions, fluid in lungs in some cases, can be controlled.

There are three general classifications of antihistamines. They are the first generation antihistamines, the second generation antihistamines and the third generation antihistamines. The first generation antihistamines are known for their many side effects including drowsiness on most patients. The second generation antihistamines, on the other hand, may also cause several side effects but they also do not normally cause drowsiness. The third generation causes the least side effects. Because of the many side effects caused by the first generation antihistamines, most doctors recommend the second and the third generation antihistamines.

Uses of Antihistamines

Antihistamines are merely used to control or alleviate the symptoms of allergic reactions and not to cure its underlying cause. Allergic reactions may include:

  • Hay fever
  • Atopic eczema
  • Allergic rhinitis
  • Urticarial
  • Allergic conjunctivitis
  • Allergic reactions due to insect stings or bites
  • Allergic reactions caused by food allergies (mild to moderate only)

Aside from treating the symptoms of allergies, antihistamines may also be used for treating certain conditions including insomnia, stomach ulcers and motion sickness.

Side Effects

It is important to note that depending on the type of antihistamine taken, patients may experience certain side effects which include:

  • Drowsiness
  • Impaired thinking
  • Dizziness
  • Dry mouth
  • Constipation
  • Dizziness
  • Blurry vision
  • Urinary retention
  • Nervousness
  • Decreased appetite
  • Headache
  • Fatigue


Before taking antihistamines, it is best to first ask your health care provider if doing so is safe for you or your child especially if having other existing medical conditions. Generally antihistamines are generally safe for most adults with no other health conditions as well as for children who are two years old and above. However, safety precautions are needed in case the patient has:

  • Epilepsy
  • Glaucoma
  • Enlarged prostate
  • Diabetes
  • Overactive thyroid
  • Heart disease
  • High blood pressure
  • Pregnant

While most antihistamines can be bought over-the-counter, you should not assume that they are safe for you. Also, even if they are safe for you, you should always consider their side effects before taking one. For instance, if you are scheduled to make a long drive, avoid taking an antihistamine as it can cause drowsiness which would make you prone to road accidents. It is best to take antihistamines when you don’t have any appointment or work that requires you to be fully awake and alert.

Also, do not abuse the use of antihistamines. Take them only when needed and as directed. Overuse and overdose of this medication may cause you to become reliant on their sedating effects.

Finally, before taking antihistamines, take time to read the information leaflet which normally comes with these medications to know their safety information. If you are not sure, seek advice from your doctor.