Difference between Decongestants and Antihistamines

Introduction - Difference between Decongestants and Antihistamines

Decongestants and antihistamines are common forms of medication. They are generally used to treat nasal congestion (stuffy nose), sneezing and runny nose triggered by common colds and allergies. Decongestants can induce insomnia, while antihistamines make one drowsy. Both the medications are available as over-the-counter or prescription drugs.

This article extensively talks about the difference between decongestants and antihistamines.

What is histamine?

Histamine is a vital chemical that plays a role in a number of distinct bodily processes. It is produced by one’s immune system and aids in getting rid of any unwanted substances. Some of its functions are:

  • Gastric acid secretion
  • Plays a role in inflammation
  • Expands blood vessels
  • Affects muscle contractions in the intestines and lungs
  • Impacts heart rate
  • Transmit messages between nerve cells
  • Helps fluids move through blood vessel walls

Histamine is also discharged if one’s body encounters a threat from an allergen. It causes the vessels to swell and dilate, resulting in allergy symptoms. Too much histamine produced by one’s body as a reaction to allergens can cause symptoms like:

  • Nasal congestion
  • Coughing
  • Breathlessness
  • Fatigue
  • Itchy skin
  • Hives
  • Other skin rashes
  • Runny nose
  • Sneezing
  • Insomnia
  • Nausea
  • Vomiting

What are decongestants?

Difference between decongestants and antihistamines

Decongestants are a form of medication that can provide one with short term relief from blocked or stuffy nose. They help one alleviate the symptoms of medical conditions like colds and flu, hay fever and other allergic reactions, catarrh and sinusitis. They function by reducing the swelling of the blood vessels in one’s nose.

What are the different dosage types of decongestants?

The different dosage types of decongestants available are:

  • Nasal sprays
  • Drops
  • Tablets or capsules
  • Liquids
  • Syrups
  • Flavored powders that dissolve in warm water

Who can take decongestants?

Decongestants can be taken by most people. But should not be used by:

  • One taking other medications
  • One with diabetes
  • One with high blood pressure
  • One with hyperthyroidism (overactive thyroid gland)
  • One with liver, kidney, heart or circulation issues
  • One with glaucoma (increased pressure in the eye)
  • One with enlarged prostate

What medical conditions are treated by decongestants?

Side effects of decongestants

The medical conditions treated by decongestants can be listed as:

  • Cough
  • Chest congestion
  • Stuffy nose caused by common cold or flu
  • Sinusitis
  • Bronchitis
  • Other respiratory ailments

How to use decongestants?

Majority of decongestants should only be used one to four times a day. One is advised to go through the patient information leaflet that comes with the medicine for instructions. One can also get it confirmed by his/her ENT specialist. It is prohibited to use decongestant nasal sprays and drops for more than a week at a time, as using them for a longer period can worsen stuffiness.

What are the side effects of decongestants?

One may experience mild side effects on using decongestants. The probable side effects are:

  • Drowsiness
  • Irritation of the lining of one’s nose
  • Headaches
  • Feeling sick
  • Dry mouth
  • Feeling agitated
  • Rash
  • Sneezing
  • Rebound congestion
  • High blood pressure
  • Rapid heartbeats
  • Seizures
  • Anxiety
  • Dizziness
  • Tremors

The side effects tend to go away once one stops taking medicines. Some of the serious side effects are hallucinations and allergic reactions (anaphylaxis).

What are antihistamines?

Dosage types of antihistamines

Antihistamines are medications frequently used to ease symptoms of allergies like:

  • Hay fever
  • Hives
  • Conjunctivitis
  • Reactions to insect bites or stings

They can also be used to prevent motion sickness and insomnia.

Antihistamines are classified into two main subtypes. The first subtype is H-1 receptor antagonists or H-1 blockers. This subtype is used to treat the symptoms of allergy. The second subtype is H-2 receptor antagonists or H-2 blockers. They are used to treat gastrointestinal conditions like:

  • Gastroesophageal reflux disease (GERD)
  • Peptic ulcers
  • Gastritis
  • Motion sickness
  • Nausea
  • Vomiting

The H-1 blocker subtype is further divided as first-generation antihistamines and second-generation antihistamine.

The first-generation antihistamines were the first type to be approved by the Food and Drug Administration (FDA). They function on histamine receptors in the brain and spinal cord in addition to other types of receptors. Most important factor about this generation of antihistamines is that they cross the blood-brain barrier, resulting in drowsiness.

Approved by the FDA, the second-generation of antihistamines came to the market in the 1980s. Unlike the first-generation, the second-generation of antihistamines does not cross the blood-brain barrier to cause drowsiness. The second-generation of antihistamines is considered safer as they do not cause drowsiness and interact with fewer drugs.

What are the different dosage types of antihistamines?

Antihistamines Dosage Image by Dr GVK Chaitanya Rao

The different dosage types of antihistamines available are:

  • Liquids
  • Lotions
  • Syrups
  • Gels
  • Eye drops
  • Tablets and capsules
  • Nasal sprays
  • Creams
  • Suppositories

Who can take antihistamines?

Antihistamines can be taken safely by most people. But should not be used by:

  • One who is pregnant or breastfeeding
  • One taking other medicines
  • One who has underlying condition (like heart disease, liver disease, kidney disease or epilepsy)

What medical conditions are treated by antihistamines?

  • Allergic rhinitis (hay fever)
  • Allergic conjunctivitis
  • Hives
  • Other skin rashes
  • Colds
  • Food allergies
  • Hypersensitivity to specific drugs
  • Insect bites and stings
  • Heartburn
  • Gastroesophageal reflux disease (GERD)
  • Duodenal and gastric ulcers
  • Zollinger-Ellison syndrome
  • Anorexia
  • Headaches
  • Anaphylaxis
  • Vertigo
  • Parkinson’s disease
  • Bone pain

How to use antihistamines?

One must take antihistamines as prescribed by his/her ENT specialist or as instructed in the patient leaflet that comes with it.

Before taking an antihistamine, one should be aware of:

  • How to take it – whether it needs to be taken with water or food or how to use it rightly
  • How much to take – dosage depends on factors like one’s age and weight
  • When to take it – frequency of the dosage and time
  • How long to take it – duration of continuing the dosage
  • What to in case of overdose
  • What to do if one misses the dose

Consult Dr G V K Chaitanya Rao – Best ENT Doctor in Hyderabad.

What are the side effects of antihistamines?

  • Drowsiness
  • Dry eyes
  • Dry mouth
  • Blurred vision
  • Double vision
  • Low blood pressure
  • Mucous discharge
  • Fast heart rate
  • Difficulty in urinating
  • Constipation
  • Headache
  • Cough
  • Tiredness
  • Sore throat
  • Abdominal pain or uneasiness
  • Nausea
  • Vomiting
  • Drowsiness
  • Joint or muscle pain
  • Headache
  • Confusion in aged people
  • Dizziness
  • Breast swelling and tenderness

Conclusion - Points of difference between decongestants and antihistamines

The difference between decongestants and antihistamines can be inferred as:

  • Decongestants – Decongestants work by blocking the effects of histamine produced in one’s body that triggers stuffy nose, itching, sneezing, runny nose and watery eyes. It mostly comes in the form of tablets and liquids. It causes side effects like drowsiness, dry mouth, dizziness, blurred vision etc.
  • Antihistamines – Antihistamines work by shrinking the blood vessels in the nose, decreasing the swelling to allow better breathing. It comes in the form of nasal sprays, tablets, nose drops, etc. it causes side effects like anxiety, insomnia, restlessness, dizziness, etc.

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Medically reviewed by SinusDoctor,
Dr G V K Chaitanya Rao

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