Often, allergies do not develop after the initial exposure. The body produces molecules known as antibodies to defend against the foreign proteins when a person is exposed to an allergen for the first time. We refer to this as an immunological reaction.
The immune system produces a lot of antibodies when an allergen is exposed repeatedly, which causes mast cells that carry histamine-containing substances to break down. This leads to the features of allergies.
Sensitization is the name given to this process. It could take days or years to become sensitized. Sensitization can sometimes happen as a person has symptoms but never fully develops an allergy to the allergen.
Symptoms of allergy include:
sneezing
shortness of breath
wheezing
runny nose and eyes
pain over the sinuses (at the bridge of the nose, near the eyes, over cheeks and at the forehead)
coughing
skin rashes (nettle rashes or hives)
swelling of the lips or face
itching eyes, ears, lips, throat and roof of the mouth
nausea
vomiting
abdominal cramps and diarrhoea
Anaphylaxis, also known as anaphylactic shock, is a severe or sometimes fatal allergic reaction. The entire body is involved in anaphylaxis.
Anaphylaxis entails
Swelling of the throat and mouth blocks airways, which makes it difficult to breathe, speak, or swallow, causes rashes and itching elsewhere on the body, and causes weakness and collapse, often with unconsciousness, as a result of a fast drop in blood pressure.Types of allergy are classified to denote cause, severity and possible management and prevention. These include –
Type I hypersensitivity
This is also known as immediate or anaphylactic-type reactions. This may be caused due to pollen, foods and drugs and insect stings.
Type II hypersensitivity
This involves specific antibodies called the Immunoglobulin G (IgG) and IgM. There is binding to and destroying the cell the antibody is bound on.
This type of reaction is seen after an organ transplant when the body refuses to see the transplanted organ as its own.
Type III hypersensitivity
This is an Immune complex-mediated reaction. The immune complex is the bound form of an antibody and an antigen.
This leads to a cascade of reactions in the body which goes on to destroy local tissues. Examples of this condition include glomerulonephritis and systemic lupus erythematous (lupus, SLE).
Type IV hypersensitivity
Delayed or cell-mediated reactions are mediated by special immune cells called the T-cell lymphocytes.
The T cells take from a few hours to a few days to mount an allergic response. Examples include contact dermatitises such as poison ivy rashes.
