Wheal and flare

What is the wheal and flare response?

The wheal and flare response is a descriptor used when talking about a two stage allergic response seen in Type 1 hypersensitivity.

The first stage, called the wheal, is controlled by substances called acute phase mediators. The second stage, called the flare, is controlled by substances called late phase mediators.

What causes the wheal and flare response to start?

The wheal and flare response is caused by an allergy. When you are exposed to something you are allergic to the wheal and flare response begins [provided it is a type I hypersensitivity reaction, which allergic rhinitis and asthma are]

Examples of substances which may cause the wheal and flare response to begin are:

• House dust mite
• Grasses
• Pollens
• Fungi
• Cats
• Dogs

What causes the wheal?

The wheal response is caused by release of histamine, which is the dominant early phase mediator. The release of histamine occurs immediately upon contact with the substance you are allergic to. The histamine is released from mast cells and causes:

• Vasodilation
• Increased permeability of blood vessels [Leaky blood vessels]

What are the symptoms of the wheal in Allergic Rhinitis?

During the wheal phase of allergic rhinitis the symptoms are:

• Itchiness around nose and eyes
• Sneezing
• Runny nose

What causes the flare?

The flare is caused by release of the late phase mediators. This occurs approximately 2 hours after you have been exposed to the allergen.  The late phase mediators are also released from mast cells and include:

• Interleukin 4
• Interleukin 5
• Leukotriene C4
• Leukotriene D4
• Leukotriene E4

What are the symptoms of the flare in Allergic Rhinitis?

The flare symptoms in allergic rhinitis are caused by the late phase mediators. These symptoms occur approximately 2 hours after exposure to the allergen. The effect of the late phase mediators are:

• Nasal congestion
• Post nasal drip
• Loss of sense of smell
• Eustachian tube dysfunction

What is the relevance to ENT?

The relevance of the wheal and flare response in ENT is mainly to do with allergic rhinitis. Allergic rhinitis is a Type 1 hypersensitivity which is characterized by a wheal and flare response.

What medications best control the wheal related symptoms?

The best medications to control the wheal response in Allergic Rhinitis are antihistamines. Antihistamines come in a variety of forms including:

• Oral antihistamines
• Intranasal antihistamines

What medications best control the flare related symptoms?

The best medications to control the flare related symptoms are intranasal steroids. The nasal steroids which are recommended for allergic rhinitis include:

• Fluticasone
• Mometasone
• Ciclesonide

Where to from here?

If you feel that you are suffering from allergic rhinitis which is not well controlled then make an appointment to see either Dr Dan Robinson or Dr Sam Dowthwaite to further discuss treatment options.

Both Dr Dan Robinson and Dr Sam Dowthwaite practice evidence based medicine in clinical practice.

Article written by Dr Dan Robinson.