Treg cells or regulatory T cells constitute a large population of cellular infiltrate in atopic/allergic inflammation and a dysregulated immune response appears to be an important pathogenetic factor. Cardinal events during allergic inflammation can be classified as activation, organ-selective homing, survival and reactivation, and effector functions of immune system cells. T cells are activated by aeroallergens, food antigens, autoantigens, and bacterial exotoxins superantigens in allergic inflammation. They are under the influence of the skin, lung, or nose-related chemokine network and show organ-selective homing. (more…)

Normally present at very low levels in plasma, antibodies of the immunoglobulin E (IgE) isotype were first discovered in 1967, decades after the description of IgA, IgG, and IM. IgE antibodies are produced primarily by plasma cells in mucosal-associated lymphoid tissue and their levels are uniformly elevated in patients suffering from atopic conditions like allergic rhinitis, asthma and atopic dermatitis. Production of allergen-specific IgE in atopic individuals is driven both by a genetic predisposition to the synthesis of this isotype as well as by environmental factors, including chronic allergen exposure. (more…)

Diagnosis of food hypersensitivity is a clinical challenge and the only current definitive test is the Double Blind Placebo-Controlled Food Challenges. Although the Double Blind Placebo-Controlled Food Challenges is the current gold standard, it is difficult to perform and is very time-consuming. Hence, researchers are continually evaluating new tests and assessing the value of the available serum tests. (more…)

Over the last 5 years some studies have suggested that the atopy patch test (APT) may be a useful test in atopic dermatitis children who have suspected food hypersensitivity and may even obviate the need for oral challenges. An alternative test to oral allergy challenges with high sensitivity and specificity would be helpful in the diagnosis of food hypersensitivity. (more…)

This study compared the diagnostic value of intradermal tests and patch tests in 20 patients with non-immediate reactions to penicillin (none had IgE antibodies to benzylpenicillin or amoxicillin detectable using a commercial RAST [radioallergosorbent test] method), using 30 patients tolerant to penicillin as controls. Intradermal tests assessed reactivity to injection of major and minor determinants of benzylpenicillin, amoxicillin and ampicillin. Allergy patch testing involved the same hapten solutions used for intradermal testing, either embedded in a patch disk or mixed with petrolatum. (more…)

Suspected drug allergy is not easy to investigate. In the UK, few centers have the necessary facilities and expertise, the evidence base of the available diagnostic tests is not robust, and their interpretation of drug allergy reaction is not straightforward. This has led many clinicians increasingly to rely on the patient’s recollection of previous response to individual allergies medicines when anticipating the likely tolerability of future exposure. (more…)

Systemic allergic reactions are a relatively common clinical emergency. In their mildest form, they may just manifest as systemic cutaneous reactions with pruritis, allergy urticaria and angioedema. In more severe cases there are cardiorespiratory symptoms such as stridor, wheeze, difficulty in breathing or hypotension. Anaphylaxis has been defined as a ‘severe, life-threatening generalized or systemic hypersensitivity reaction’. The prevalence of systemic allergic reactions is unclear because of the lack of a clear, consistent definition and large prospective population studies. (more…)

Allergy skin testing is probably the most susceptible and practical way to monitor for existing allergy sensitivity. Biological extracts of aeroallergens such as trees, dust mites, weeds, cockroaches, molds, and animal danders are offered for allergy testing. The most common and approved way to test is by putting a drop of antigen on the surface area of the patient’s skin and scratching or skin prick test with a lancet or sharp object. The most essential ancillary test to confirm the diagnosis of allergy is the skin test, which is the gold standard in this respect. The skin test final results must be viewed in light of the history to decide the importance of a positive test. (more…)

By definition, allergy is a condition where a person has hypersensitivity to an environmental, drug, or food antigen (allergen) caused by an altered or unusual immune system reaction to the antigen.

Allergenic foods can impact the lungs when an allergic reaction individual inhales food particles that may have been released when the food was cooked or that were dispersed in aerosol form. Allergy to the allergens in cooked food has been reported by highly allergic patients who were exposed to their allergenic foods (say, fish, shellfish, or eggs) in an enclosed area (for example, a restaurant dining room) or during meal preparation. Most cases of asthma triggered by aerosolized food allergens involve adults engaged in specific occupations that regularly expose them to the allergens. In contrast, most cases of asthma in children are triggered when the allergen is eaten, not inhaled.

Many experts believe that if a baby can be protected from becoming sensitized to the most highly allergenic foods when their healthy immune system and the digestive tract are in the most vulnerable stage for allergy to develop, the incidence of lifelong food allergy and potentially life-threatening anaphylactic reactions to foods will be reduced and hopefully entirely prevented. When a baby has been identified to be at risk for developing allergy, measures to reduce allergic sensitization might be implemented at birth and the problems associated with future food allergy may be significantly reduced. However, as we shall see in later discussions, experts disagree on the best way to avoid this early allergic sensitization.

The reaction of asthmatics to these chemical compounds is not an allergy, but is more correctly described as allergy intolerance because the initial response is not a triggering of the immune system. The process involves an increase in the level of the inflammatory mediators that are responsible for the bronchospasm of asthma. These mediators include histamine and leukotrienes. They are released during the reaction to an allergen, and cause the muscular contractions that result in the difficulty in breathing and wheezing that are typical of asthma. By inhibiting (or turning off) other types of mediators, the chemicals in the food additives cause an increase in the level of antihistamine and leukotrienes. This results in increased bronchospasm, and a definite worsening of the asthma symptoms.

Oral allergy syndrome is an allergic reaction to food that is confined to the oral cavity (i.e., to the lips, and around the lips, roof of the mouth, tongue, hard and soft palate, and uvula) and adjacent structures. It differs from other food allergy in that its symptoms do not appear in any other location in the body, and always accompany respiratory allergy to inhaled allergens of plants, particularly plant pollens. Of course, symptoms in the mouth, throat, and upper respiratory tract can be part of a generalized reaction to foods, but in this case they are more accurately described as oral allergy symptoms. The term oral allergy syndrome applies specifically to pollen allergy (pollinosis) accompanied by reactions to certain raw foods when they are in direct contact with oral tissues. Individuals with Oral allergy syndrome typically have hay fever symptoms caused by allergies to trees, grasses, and weeds. They experience irritation in the mouth (lips, tongue, roof of the mouth) and sometimes the throat after eating specific types of raw fruits, vegetables, and sometimes nuts.

Definitions of anaphylaxis vary considerably, impeding the comparison of different clinical studies. Different definitions of anaphylaxis have been developed as clinical descriptions of severe allergic reactions, different authors emphasizing different symptoms.

The author aimed to develop a simple clinical grading system and definition for anaphylaxis using clinical data. He retrospectively analyzed 1149 case records (median age 29 years) with systemic allergic reactions (30% venom allergy, 22% iatrogenic allergy, 18% food allergy) from an emergency department in Australia. (more…)