hypersensitivity

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Related to flea bite hypersensitivity: Flea allergy dermatitis

hypersensitivity

 [hi″per-sen″sĭ-tiv´ĭ-te]
a state of altered reactivity in which the body reacts with an exaggerated immune response to a foreign agent; anaphylaxis and allergy are forms of hypersensitivity. The hypersensitivity states and resulting hypersensitivity reactions are usually subclassified by the Gell and Coombs classification. adj., adj hypersen´sitive.
contact hypersensitivity that produced by contact of the skin with a chemical substance having the properties of an antigen or hapten.
delayed hypersensitivity (DH) (delayed type hypersensitivity (DTH)) the type of hypersensitivity exemplified by the tuberculin reaction, which (as opposed to immediate hypersensitivity) takes 12 to 48 hours to develop and which can be transferred by lymphocytes but not by serum. Delayed hypersensitivity can be induced by most viral infections, many bacterial infections, all mycotic infections, and a few protozoal infections (leishmaniasis and toxoplasmosis). The scope of the term is sometimes expanded to cover all aspects of cell-mediated immunity including contact dermatitis, granulomatous reactions, and allograft rejection.
immediate hypersensitivity antibody-mediated hypersensitivity occurring within minutes when a sensitized individual is exposed to antigen; clinical manifestations include systemic anaphylaxis and atopic allergy (allergic rhinitis, asthma, dermatitis, urticaria, and angioedema). The first exposure to the antigen induces the production of IgE antibodies (cytotropic antibodies, reagin) that bind to receptors on mast cells and basophils. Subsequent exposure to the antigen triggers production and release of a diverse array of mediators of hypersensitivity that act on other cells producing symptoms such as bronchospasm, edema, mucous secretion, and inflammation.
hypersensitivity reaction the exaggerated or inappropriate immune response occurring in hypersensitivity, in response to a substance either foreign or perceived as foreign and resulting in local or general tissue damage. Such reactions are usually classified as types I–IV on the basis of the Gell and Coombs classification.

hy·per·sen·si·tiv·i·ty

(hī'pĕr-sen'si-tiv'i-tē),
1. Abnormal sensitivity, a condition in which there is an exaggerated response by the body to the stimulus of a foreign agent.
2. In endocrinology, an excessive target tissue response to a hormone. Synonym(s): hormone hypersensitivity

hypersensitivity

/hy·per·sen·si·tiv·i·ty/ (-sen″sĭ-tiv´ĭ-te) a state of altered reactivity in which the body reacts with an exaggerated immune response to what is perceived as a foreign substance. The hypersensitivity states and resulting reactions are usually subclassified by the Gell and Coombs classification (q.v.).hypersen´sitive
antibody-mediated hypersensitivity 
1. type II h.; see Gell and Coombs classification, under classification.
2. occasionally, any form of hypersensitivity in which antibodies, rather than T lymphocytes, are the primary mediators, i.e., types I–III.
cell-mediated hypersensitivity  type IV h.; see Gell and Coombs classification, under classification.
contact hypersensitivity  a type IV hypersensitivity produced by contact of the skin with a chemical substance having the properties of an antigen or hapten.
cytotoxic hypersensitivity  type II h.; see Gell and Coombs classification, under classification.
delayed hypersensitivity  (DH), delayed-type hypersensitivity (DTH) that which takes 24 to 72 hours to develop and is mediated by T lymphocytes rather than by antibodies; usually used to denote the subset of type IV hypersensitivity involving cytokine release and macrophage activation, as opposed to direct cytolysis, but sometimes used more broadly, even as a synonym of type IV h.
immediate hypersensitivity 
1. type I h.; see Gell and Coombs classification, under classification.
2. occasionally, any form of hypersensitivity mediated by antibodies and developing rapidly, generally in minutes to hours (i.e., types I–III ), as distinguished from that mediated by T lymphocytes and macrophages and requiring days to develop (type IV, or delayed h. ).
immune complex–mediated hypersensitivity  type III h.; see Gell and Coombs classification, under classification.
T cell–mediated hypersensitivity  type IV h.; see Gell and Coombs classification, under classification.
type I hypersensitivity  see Gell and Coombs classification, under classification.
type II hypersensitivity  see Gell and Coombs classification, under classification.
type III hypersensitivity  see Gell and Coombs classification, under classification.
type IV hypersensitivity  see Gell and Coombs classification, under classification.

hypersensitivity

[-sen′sətiv′itē]
Etymology: Gk, hyper + L, sentire, to feel
an abnormal condition characterized by an exaggerated response of the immune system to an antigen. See also allergy. hypersensitive, adj.

hypersensitivity

Immunology An abnormal immune response that may be immediate–due to antibodies of the IgE class, or delayed–due to cell-mediated immunity. See Cold hypersensitivity, Immediate hypersensitivity Neurology Exaggerated sensitivity An ↑in a person's sensitivity to light, sound, smell, taste, touch, temperature, balance, and even emotional issues, which may be linked to anxiety and panic disorders.

hy·per·sen·si·tiv·i·ty

(hī'per-sen'si-tiv'i-tē)
Abnormal sensitivity, a condition in which there is an exaggerated response by the body to the stimulus of a foreign agent.
See: allergy

hypersensitivity

An allergic state in which more severe tissue reactions occur on a second or subsequent exposure to an ANTIGEN than on the first exposure. A particular group of antibodies (IgE) is involved in many hypersensitivity reactions.

hypersensitivity

the process of localized plant cell death that occurs immediately after entry of a cell by a plant pathogen. Such a reaction can act as a host-resistance mechanism since the cell death often prevents further growth of biotrophic pathogens, e.g. powdery mildews or rusts.

Hypersensitivity

After the body's immune system attacks an outside invader (such as organic dust or a fungus) many times, exposure to even a tiny amount of this allergen can provoke a strong inflammatory response.

hypersensitivity

marked sensitivity/reactivity to innocuous stimuli

hypersensitivity

An excessive reaction, local or systemic, or inappropriate immune response to an antigen. Four types of immune responses are usually described, but the main reaction involving the eyes is type 1. They are also called allergic reactions types 1-4.
type 1 hypersensitivity An immediate, abnormal reaction occurring when an antigen reacts with an antibody (e.g. immunoglobulin E (IgE)) attached to a mast cell or basophil. This leads to the release of specific chemical mediators of allergy (e.g. histamine) that react with target organs throughout the body. Systemic signs include: itching, lacrimation, skin rash and possibly haemodynamic collapse and shock. Allergic conjunctivitis is an example of this type of hypersensitivity.
Type 2 h . (cytotoxic h.) is caused by an interaction of antibody and antigens on cell surfaces. Examples: Graves' disease, myasthenia gravis. Type 3 h. (immune-complex mediated h.) is mediated by a combination of antigen-antibody. Example: systemic lupus erythematosus. Type 4 h. (T cell-mediated h.) is a delayed reaction (several days to develop) mediated by T lymphocytes. Example: rheumatoid arthritis. See antihistamine; mast cell stabilizers.

hy·per·sen·si·tiv·i·ty

(hī'per-sen'si-tiv'i-tē)
In endocrinology, an excessive target tissue response to a hormone.

hypersensitivity,

n 1. an adverse reaction to contact with specific substances in quantities that usually produce no reaction in normal individuals.
n 2. an allergic tendency. In general, a tendency to react with unusual violence to stimuli.
n 3. a common complaint after periodontal therapy in which dentin may be exposed, resulting in pain in the teeth or sensitivity to heat, cold, and sweet substances.
Enlarge picture
Contact hypersensitivity.
hypersensitivity, atopic,
n See atopy.
hypersensitivity, bacterial,
n delayed inflammatory reaction resulting from previous sensitization of the host by an antigen.
hypersensitivity, delayed,
n a type involving a latent period between the antigen introduction and the reaction; cellular reactions mediated by the T lymphocytes (e.g., tuberculosis, and transplant reaction).
hypersensitivity, dentin,
n refers to the pain caused by fractures, or gingival recession, which exposes the dentin of a tooth. This condition requires immediate treatment and can be corrected with topical agents or with periodontal or restorative procedures, such as gingival grafts or enamel bonding.
hypersensitivity, immediate,
n a humoral reaction, mediated by the circulating B lymphocytes, which causes any of three immediate responses: anaphylactic hypersensitivity, cytotoxic hypersensitivity, and immune system hypersensitivity.
hypersensitivity reaction, cytotoxic,
n a reaction in which the surface antigens of a cell join with an antibody, causing complement-mediated cell destruction, or other types of cell-membrane damage.
hypersensitivity reactions, immune complex,
n.pl one of four types of hypersensitivity reactions to antigens in the body that acts as a barrier to disease. The reactions can cause tissue damage.

hypersensitivity

1. a state of altered reactivity in which the body reacts with an exaggerated immune response to a foreign agent; allergy is a synonym for hypersensitivity. anaphylaxis is a form of hypersensitivity.
There are four basic types of hypersensitivity reactions: Type I (called also immediate hypersensitivity) involves cell-fixed antibody, mainly IgE attached to mast cells or basophils. Antigen binding causes the cell to release vasoactive factors. The basis for anaphylaxis and atopy. Type II causes cell destruction (cytotoxicity) by the action of immunoglobulin with complement or cytotoxic cells. Seen in red blood cell transfusion reactions and in alloimmune hemolytic anemia. See also antibody-dependent cellular cytotoxicity. Type III (called also immune-complex or subacute hypersensitivity) causes tissue damage and inflammation by the deposition of antigen-antibody complexes that activate complement and attract polymorphonuclear cells. Type IV (called also delayed hypersensitivity) involves sensitized T lymphocytes that react with cell bound or associated antigen and release lymphokines, causing mononuclear cell accumulation, tissue damage and inflammation, typically manifesting at least 24 hours after exposure to the antigen.
2. a state of increased responsivity to physical stimuli.

hypersensitivity angiitis
variant of polyarteritis nodosa; a disease of small blood vessels in humans; called also leukocytoclastic vasculitis.
antibody-mediated hypersensitivity
types I, II and III hypersensitivity reactions. Called also immediate hypersensitivity.
bacterial hypersensitivity
immune responses to bacteria or bacterial products may contribute to the clinical features of some diseases, e.g. the anemia associated with salmonellosis, arthritis in erysipelas of pigs, intestinal lesions in Johne's disease, or be the principal cause as in staphylococcal hypersensitivity dermatitis in dogs.
contact hypersensitivity
a type IV reaction produced by contact of the skin with a low-molecular-weight chemical substance having the properties of a hapten in a sensitized individual; it includes allergic contact dermatitis.
cutaneous basophil hypersensitivity
a delayed inflammatory response characterized by large numbers of basophils.
cytotoxic hypersensitivity
type II hypersensitivity.
delayed hypersensitivity
type IV reaction. A slowly developing cell-mediated immune response in which T helper 1 lymphocytes respond to specific antigen by releasing cytokines, some of which activate macrophages, as occurs in tuberculin reaction, graft rejection, some autoimmune diseases, etc.
drug hypersensitivity
may be either an immediate (antibody mediated) or delayed type (T lymphocyte mediated) reaction. See also drug eruption.
flea bite hypersensitivity
see flea allergy dermatitis.
food hypersensitivity
hypersensitivity reaction to various dietary constituents has been the suspected cause of allergic dermatitis in most species, but conclusive evidence is often lacking. It may also result in diarrhea.
fungal hypersensitivity
may contribute to the clinical features of cutaneous fungal infections, particularly kerion formation. It is also the basis for skin testing for systemic mycoses, e.g. histoplasmin and coccidioidin.
helminth hypersensitivity
occurs, e.g. the self-cure phenomenon, and the allergic response of a sensitized animal to an invasion, e.g. of lungs, causes massive pulmonary edema.
immediate hypersensitivity
antibody-mediated hypersensitivity, i.e. types I, II and III, characterized by a response that appears within minutes to hours, resulting either from a release of histamine and other mediators of hypersensitivity from IgE-sensitized mast cells, causing increased vascular permeability, edema and smooth muscle contraction (type I), from antibody-mediated lysis of red blood cells (type II), or from immune complex mediated pathology (type III).
immune complex hypersensitivity
type III hypersensitivity (above).
mold hypersensitivity
see acute bovine pulmonary emphysema-edema.
hypersensitivity pneumonitis
see hypersensitivity pneumonitis.
staphylococcal hypersensitivity
see bacterial hypersensitivity (above).
hypersensitivity threshold
a theory that certain levels of allergens may be tolerated by some sensitized individuals without manifestations of disease, but a slight increase in the level precipitates clinical signs.
tuberculin type hypersensitivity
the classical T lymphocyte cell-mediated hypersensitivity associated with mycobacterium infection or immunization with antigens containing Freund's adjuvant.

Patient discussion about hypersensitivity

Q. ALLERGIES what are they,who gets them,are they caused by pollen and food?

A. Allergy is the exaggerated and out-of-place reaction of the immune system to external substances or stimuli that are not harmful to the body, so the reaction actually damages the body instead of helping it.

The may be pollen and foods, as well as insect stings, drugs and almost any other substances.

You may read more here:
www.nlm.nih.gov/medlineplus/allergy.html
http://www.mayoclinic.com/health/allergy/AA99999

Q. what is the most common allergy? is it dust allergy?

A. thanks, I've heard of a new allergy treatment and trying to learn some more about the different kinds...

Q. what are the symptoms of Allergy?

A. from you question i understand that you think you might developed an allergy. so here is a web page with couple of videos explaining about allergies:
http://www.healthline.com/video/allergies

More discussions about hypersensitivity