Edit concept Question Editor Create issue ticket


Allergic Reaction

An allergy is defined as an immune response induced by exposure to an allergen. Austrian pediatrician Clemens Pirquet first used the term allergy in 1906. Hypersensitivity reactions can be divided into four groups: type I, type II, type III and type IV, based on the mechanisms involved.


Symptoms of type1 hypersensitivity reactions might vary from mild to severe. Allergen exposure in the beginning might cause mild symptoms, which might get worse when exposed to the allergen. Symptoms of the mild allergic reaction include itching, rashes, hives, nasal congestion, rhinorrhea, sneezing, dyspnea, wheezing and itchy eyes.

  • All participants with immunologically confirmed hypersensitivity reactions had multiple symptoms: about two-thirds had the presence of at least three symptoms (fever, rash, plus another systemic symptom) and a third consisted of fever plus rash alone.[aidsmap.com]
  • On the second occasion, re-introduction resulted in whole body rash 4 h post dose and was associated with fever, respiratory symptoms, headache and vomiting. On examination, he was pyrexic, tachyponeic, tachycardiac and hypotensive.[ncbi.nlm.nih.gov]
  • These reactions often cause chronic joint or muscle pain, inflammation, and swelling, leading to generalized fatigue and lack of energy.[medbroadcast.com]
  • Compassion Fatigue Hypersensitivity can also be symptomatic of a serious psychological condition called Compassion Fatigue, which I discussed in Part I, Endnote 1.[lifelongactivist.com]
  • : Supplementation and sun exposure Muskuloskeletal health Heart health Cancer Autoimmune conditions Mental health Developmental disorders Pregnancy and fertility Aging Fitness and exercise Gastrointestinal health Asthma Infections Everyday aliments: fatigue[vitamindcouncil.org]
  • Symptoms appear relatively suddenly and include: Fever Chills Fatigue Breathlessness Chest tightness Cough If the person is removed from the antigen exposure, the symptoms usually resolve over 24 to 48 hours. Recovery is often complete.[ucsfhealth.org]
  • Clinical Spectrum The most common symptoms of abacavir hypersensitivity are fever, rash, nausea, vomiting, diarrhea or abdominal pain, and fatigue and malaise [ 53 ].[cid.oxfordjournals.org]
  • ., tachycardia, hypotension, myalgia, fatigue, pain, malaise, dizziness, and headache), findings that are consistent with those previously reported.[nejm.org]
  • Adults — signs and symptoms Chronic diarrhea (formerly considered the most common symptom) Weight loss Iron-deficiency anemia Abdominal distension due to bloating Malaise and fatigue Edema (hypoproteinemia) Osteoporosis Children — signs and symptoms Failure[worldgastroenterology.org]
Wound Infection
  • The use of skin adhesives in place of traditional sutures is increasing in popularity given Dermabond's potential benefits of decreased wound infection rate and better wound approximation.[ncbi.nlm.nih.gov]
  • Symptoms: Some of the symptoms of type1 hypersensitivity are nasal congestion, sneezing, wheezing, rashes, hives and itchy eyes.[symptoma.com]
  • People who have dust allergies are familiar with sneezing—but sneezing isn’t the only uncomfortable symptom. Learn the signs and symptoms of different types of insect sting allergy. Discover treatment options through ACAAI.[acaai.org]
  • Metal hypersensitivities have a delayed onset from the time of exposure to the materials and are not caused by specific antibodies or histamine release that lead to the classical indications of a common allergy like itching, watery eyes, or sneezing.[center4research.org]
  • This results in allergy symptoms such as sneezing, mucus production, swelling, itching, runny nose, coughing, and wheezing. Credit: NIAID[web.archive.org]
  • A 6, 13 Azelastine (Astelin) may be used for vasomotor rhinitis associated with rhinorrhea, sneezing, postnasal drip, and nasal congestion.[aafp.org]
  • Nausea, vomiting, diarrhea, or stomach pain. Generally ill feeling, extreme tiredness, or aches. Shortness of breath, cough, or sore throat.[i-base.info]
  • Symptoms of EHS EHS is characterized by a collection of non-specific symptoms, such as: Skin disturbances (redness, tingling and burning sensations) Neurological issues (fatigue, difficulty concentrating, dizziness) Headaches and nausea Chest pain Blood[care2.com]
  • Respiratory: nasal congestion, cough, sneezing, hoarseness, chest tightness, dyspnea (due to bronchospasm or laryngeal edema ) Cardiovascular: hypotensio n, tachycardia, chest pain (myocardial ischemia due to hypoxia and hypotension ) GI: abdominal pain, nausea[amboss.com]
  • When the food enters the stomach and then the intestines, nausea, cramping, pain, vomiting and diarrhea may occur. Body systems, such as the skin, lungs and blood vessels, that are affected after the food leaves the digestive tract.[web.archive.org]
  • ES is claimed by believers to present itself either directly in the crank "patient" as some unspecific form of nausea or tingling (or some other vague fever symptom), or — more asymptomatically — as an alleged long-term cancer hazard.[rationalwiki.org]
Abdominal Pain
  • There was a statistically significant difference in both GSRS (total and component) and GOS scores at baseline between patients testing ( ) and (-) on food allergen testing, mainly for diarrhoea (p 0.001), abdominal pain (p 0.001) and indigestion p CONCLUSIONS[ncbi.nlm.nih.gov]
  • pain, diarrhea, nausea/vomiting Lymphadenopathy Course Symptoms appear 1–2 weeks following initial exposure.[amboss.com]
  • If you have gluten sensitivity, you may have symptoms similar to those of celiac disease, such as abdominal pain and tiredness. Unlike celiac disease, gluten sensitivity does not damage the small intestine.[niddk.nih.gov]
  • Eating something you are allergic to can cause nausea, vomiting, abdominal pain, cramping, diarrhea, or a severe, life-threatening reaction. Allergens that touch the skin can cause a skin rash, hives, itching, blisters, or skin peeling.[nlm.nih.gov]
  • […] containing animal protein s or serum ( “serum” sickness) Medication s, most frequently antibiotics ( penicillin, amoxicillin, cefaclor, and trimethoprim-sulfamethoxazole ) Infections: Hepatitis B virus Clinical features Fever Rash ( urticarial or purpuric ) Arthralgias[amboss.com]
  • Drug-Related Hypersensitivity Hypersensitivity to medication is a life-threatening reaction that results in a systemic illness that usually includes fever and maculopapular rash accompanied by constitutional symptoms (fatigue, malaise, myalgias, and arthralgias[cid.oxfordjournals.org]
  • […] followed the grading system proposed in the Position Paper of the European Academy of Allergology and Clinical Immunology on Immunotherapy ( Malling 1993 ): Grade 1: Non‐specific reactions: Reactions probably not IgE‐mediated; i.e. discomfort, headache, arthralgia[doi.org]
  • 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.[medical-dictionary.thefreedictionary.com]
  • Symptoms are urticaria, coughing, rhinorrhoea, lacrimation, abdominal cramps, pruritus, a burning sensation, angioedema, dyspnoea and even circulatory collapse and death.[revistanefrologia.com]
  • Symptoms consist of redness (mainly due to vasodilation of the peripheral small blood vessels), edema (swelling) of the conjunctiva, itching, and increased lacrimation (production of tears).[waojournal.biomedcentral.com]
Red Eye
  • Allergy Hives are a common allergic symptom Specialty Immunology Symptoms Red eyes, itchy rash, runny nose, shortness of breath, swelling, sneezing [1] Types Hay fever, food allergies, atopic dermatitis, allergic asthma, anaphylaxis [2] Causes Genetic[en.wikipedia.org]
Eye Swelling
  • Symptoms of allergic rhinitis and asthma include the following: Runny nose and mucus production Sneezing Itchy nose, eyes, ears, and mouth Stuffy nose Red and watery eyes Swelling around the eyes Coughing Wheezing Chest tightness Shortness of breath To[web.archive.org]
  • The composition of the intestinal microflora may be different in those with atopic eczema, and such differences may precede the development of eczema.[doi.org]
  • Among 27 possible risk factors assessed, statistically significant associations included recurrent epistaxis, easy bruising, hypersensitivity (eczema, hives, hay fever, and rhinitis), previous treatment with sclerotherapy or endovenous laser for lower[ncbi.nlm.nih.gov]
  • "In hypersensitive individuals, fluorides occasionally cause skin eruptions such as atopic dermatitis, eczema or urticaria. Gastric distress, headache and weakness have also been reported.[fluoridealert.org]
  • Conclusions Consumption of n-3 and n-6 PUFAs, especially α-linolenic acid and linoleic acid, may be positively associated with eczema. Arachidonic acid intake may be inversely related to eczema and rhinoconjunctivitis.[bmcpublichealth.biomedcentral.com]
  • The authors present 2 case reports of selective cefazolin hypersensitivity: a 49 year-old woman with a history of two perioperative reactions (urticaria and severe anaphylaxis) after the use of rocuronium, propophol and cefazolin; a 36 year-old pregnant[ncbi.nlm.nih.gov]
  • These skin reactions include perioral dermatitis, stomatitis, and urticaria.[fluoridealert.org]
  • […] selective cefazolin hypersensitivity: a 49 year-old woman with a history of two perioperative reactions (urticaria and severe anaphylaxis) after the use of rocuronium, propophol and cefazolin; a 36 year-old pregnant woman who developed facial erythema, lips angioedema[ncbi.nlm.nih.gov]
  • Recommended Related to Allergies Angioedema, Hereditary Important It is possible that the main title of the report Angioedema, Hereditary is not the name you expected.[web.archive.org]
  • The eruption returned with successive alemtuzumab infusions (infusions 19, 20 and 21), remained present for longer and was more severe with each infusion.[ncbi.nlm.nih.gov]
  • "In hypersensitive individuals, fluorides occasionally cause skin eruptions such as atopic dermatitis, eczema or urticaria. Gastric distress, headache and weakness have also been reported.[fluoridealert.org]
Subcutaneous Nodule
  • We present a case of persistent subcutaneous nodules and sterile abscesses in the setting of delayed type hypersensitivity to aluminum, confirmed by patch testing and recurrence on re-exposure.[ncbi.nlm.nih.gov]
Pelvic Pain
  • CASE: A 41-year-old woman with chronic pelvic pain and previous ketamine exposure developed a widespread urticarial rash and mild perioral edema following the initiation of a ketamine infusion.[ncbi.nlm.nih.gov]
  • On the second occasion, re-introduction resulted in whole body rash 4 h post dose and was associated with fever, respiratory symptoms, headache and vomiting. On examination, he was pyrexic, tachyponeic, tachycardiac and hypotensive.[ncbi.nlm.nih.gov]
  • For example, a headache might tell you that you're coming down with a cold, or that you've had too much caffeine. Dizziness may indicate the onset of stomach flu, or a lack of sleep.[livescience.com]
  • Gastric distress, headache and weakness have also been reported. These hypersensitivity reactions usually disappear promptly after discontinuation of the fluoride.”[fluoridealert.org]
  • […] and sun exposure Muskuloskeletal health Heart health Cancer Autoimmune conditions Mental health Developmental disorders Pregnancy and fertility Aging Fitness and exercise Gastrointestinal health Asthma Infections Everyday aliments: fatigue, pain and headaches[vitamindcouncil.org]
  • […] condition of sound sensitivity (Hyperacusis) “ ” Electromagnetic hypersensitivity disorder — people who believe they have sensitivity to electronic devices claim that electronic signals from WiFi, cellphones and even television can cause them to experience headaches[rationalwiki.org]


Diagnosis of type1 hypersensitivity involves clinical evaluation, evaluating serum IgE levels and complete blood count, skin testing, allergen specific serum IgE testing, ophthalmic testing, nasal and bronchial challenge and provocative testing. Knowing the details of history of the disease is more important than testing procedures. Details about history include duration and frequency of allergic attacks, identifiable triggering factors, relation to settings, responses to attempted treatments and family history of atopic disorders [7].


Treatment of type1 hypersensitivity reactions include administering antihistamine medications after the allergen is eliminated from the body. Severe hypersensitivity reactions would require a therapy that involves oxygen provision for resolving breathing difficulties. Anaphylactic shock will be managed with intravenous fluids to boost blood pressure. Very severe reactions would require hospitalization. Drugs like mast cell stabilizers, H1 blockers, immunotherapy, and anti-inflammatory corticosteroids and leukotriene inhibitors are also used for treating type1 hypersensitivity reactions [8, 9].


Prognosis of type1 hypersensitivity reactions constitute hives, anaphylaxis, swelling and breathing difficulties that usually improve in few minutes to few hours. Some rashes require many days to heal and a vigorous allergic reaction might require an overnight stay in the hospital. Continued exposure to the allergens might require continued medical therapy. Inhaled or ingested allergens may require a few days to get eliminated from the body [6].


Allergic or type1 hypersensitivity reactions occur with the interference of IgE. These reactions are caused by opiates, iodinated radiocontrast dye, and vancomycin and appear similar to the urticaria or anaphylaxis. Patients affected by these types of reactions are called Atopic. Atopy is the condition where the patient is genetically predisposed to synthesize IgE antibodies against the allergens.

If allergy is present in a close relative of the patient, then the patient has higher risk of developing allergy. There are no specific causes for allergic hypersensitivity. But, a few reasons are considered as possible causes of this disease. They are pet dander, foods like nuts or shell fish, insect bites, drugs like penicillin or aspirin, some plants and pollen [2]. Relationship between HLA loci and atopy, polymorphism in certain genes that include IgE receptor beta chain, IL-4 receptor alpha chain, CD14, disintegrin are some of the genetic factors that lead to type1 hypersensitivity reactions. Type2 cell-directed immune responses are maintained by the interaction of environmental factors with the genetic factors. The other site specific factors such as adhesion molecules in bronchial epithelium and gastrointestinal tract, and skin, direct the type2 helper cells to the target tissues.


It has been observed that  individuals affected by atopic diseases have increased from the year 2000 in the United States. Allergic rhinitis is considered the most widespread affecting 17 to 22 percent of the population. It was estimated that Asthma affected nearly 25 million people in the United States in the year 2010. Predominance of asthma has increased from 7.3 percent in 2001 to 8.4 percent in 2010. Asthma affecting 90 percent of children was found to be due to allergy, while 50 to 70 percent of adults were affected by allergic asthma. According to an epidemiological research program, allergic rhinoconjunctivitis was predominant in children in 56 countries [3].

Sex distribution
Age distribution


Immediate hypersensitivity reactions are driven by IgE. The development of these antibodies is driven by T and B cells. CD4+ T cells are classified into 3 groups called effector T cells, T-regulatory cells and memory T-cells. Effector T-cells are again classified into T-Helper1, T-Helper 2 and T-Helper 17 depending on the cytokines they produced. Cell-mediated immune response is triggered by TH1 cells. TH2 cells synthesize Interleukin-4 and Interleukin-3 that stimulate B-cells producing antigen specific IgE. T-Helper 17 cells produce a set of interleukins to enhance neutrophil inflammation required for immunity in the skin and mucosa, and to produce antimicrobial peptides. The allergen that is ingested is managed by antigen presenting cell, such as B-cell. These cells later get transferred to lymph nodes appearing as naïve TH cells bearing receptors for a particular antigen [4, 5].


People can identify the specific allergens which trigger the inflammatory reaction and learn to avoid them. Types of allergy tests conducted by the specialists include skin testing, blood tests, and checking for the allergic reactions by certain allergens. The identified allergens are then avoided to prevent allergies [10].


The immune reactions that occur in the human body as protection to the body against diseases can sometimes result in reactions that damage the host itself. These reactions are known as hypersensitivity reactions. Immunopathology is the study of hypersensitivity reactions. There are four mechanisms of hypersensitivity. Type1 is also called immediate hypersensitivity and is IgE-mediated or called common allergy. Type2 reactions are cytotoxic and they are mediated by antibody and cellular mechanisms. Type3 reactions include antigen and antibody complex formations. These complexes attach the red blood cells and help in removing them by phagocytosis, release cytokines, stimulate inflammation in tissue spaces and activate T-cells. Type4 reactions are cell mediated, take more than 12 hours to develop and depend on antigen and T-cell interaction leading to inflammation. Allergy is also a hypersensitivity disorder caused by external antigenic substances. As the types of hypersensitivity vary, the etiology of allergic reactions as example is discussed here [1].  

Patient Information

  • Definition: Hypersensitivity reactions are the immune reactions that arise due to the disease antigens, and damage the cells in the body. These reactions have four different types of mechanisms in managing immunity against the ingested foreign particle. 
  • Cause: Some of the causes of type1 hypersensitivity reactions include genetic factors, environmental factors and site specific factors like adhesion molecules to bronchial epithelium and gastrointestinal tract. Genetic factors include HLA loci and polymorphism in some genes. Environmental factors include endotoxins, viral and bacterial infections that usually hinder T-helper2 cells and discourage allergic responses.
  • Symptoms: Some of the symptoms of type1 hypersensitivity are nasal congestion, sneezing, wheezing, rashes, hives and itchy eyes
  • Diagnosis: Diagnostic tests for type1 hypersensitivity include skin testing, serum IgE testing, ophthalmic testing, provocative testing, and nasal and bronchial challenge. 
  • Treatment:Treatment of this disease includes use of antihistamines and administering intravenous fluids to enhance blood flow in the anaphylactic shocks. The drugs used for treating severe disease are H1 blockers, anti-inflammatory corticosteroids, immunotherapy, mast cell stabilizers and leukotriene inhibitors



  1. Lawlor GJ, Fischer TJ, Adelman DC, eds. Manual of Allergy and Immunology. 3rd ed. Philadelphia, Pa: Lippincott-Raven; 1995.
  2. Birnbaum J, Vervloet D. Allergy to muscle relaxants. Clin Rev Allergy 1991; 9:281.
  3. Schoenwetter WF. Allergic rhinitis: epidemiology and natural history. Allergy Asthma Proc. Jan-Feb 2000;21(1):1-6.
  4. Middleton E, Reed C, Ellis E, eds. Allergy: Principles and Practice. 5th ed. St. Louis, Mo: Mosby-Year Book; 1998.
  5. Pichler WJ. Delayed drug hypersensitivity reactions. Ann Intern Med 2003; 139:683.
  6. Janson C, Anto J, Burney P, et al. The European Community Respiratory Health Survey: what are the main results so far? European Community Respiratory Health Survey II. Eur Respir J. Sep 2001;18(3):598-611.
  7. Bernstein JA, Lang DM, Khan DA, Craig T, Dreyfus D, Hsieh F, et al. The diagnosis and management of acute and chronic urticaria: 2014 update. J Allergy Clin Immunol. May 2014;133(5):1270-7
  8. Stock P, DeKruyff RH, Umetsu DT. Inhibition of the allergic response by regulatory T cells. Curr Opin Allergy Clin Immunol. Feb 2006;6(1):12-6.
  9. Weber RW. Immunotherapy with allergens. JAMA. Dec 10 1997;278(22):1881-7.
  10. Lasley MV. Allergic disease prevention and risk factor identification. Immunol Allergy Clin North Am. 1999;19:149-59.

Ask Question

5000 Characters left Format the text using: # Heading, **bold**, _italic_. HTML code is not allowed.
By publishing this question you agree to the TOS and Privacy policy.
• Use a precise title for your question.
• Ask a specific question and provide age, sex, symptoms, type and duration of treatment.
• Respect your own and other people's privacy, never post full names or contact information.
• Inappropriate questions will be deleted.
• In urgent cases contact a physician, visit a hospital or call an emergency service!
Last updated: 2019-07-11 21:42