Anaphylaxis is a potentially fatal allergic reaction. Anaphylaxis is most commonly caused by a prescription drug or food allergy, but in many instances there is no known cause. The highest rates of anaphylaxis in humans occur in early childhood and are associated with food allergy. Latex allergy, pharmaceutical drugs, and stinging insect reactions are important later in childhood, with drug allergy peaking in adult populations.

In an allergic reaction the immune system overreacts to an allergen, releasing chemicals that cause symptoms in one area of the body, such as hives or an itchy feeling in the mouth or throat. In a serious reaction, known as anaphylaxis, the reaction affects more of the body and may include worrisome symptoms such as difficulty breathing, wheezing or throat swelling.

Anaphylaxis Treatment
If an anaphylaxis reaction occurs, the drug of choice, which should be administered immediately, is epinephrine. Although there is some debate as to the preferred injection site, it is clear that of sites studied to date, injection in the lateral thigh (vastus lateralis) produces the most rapid rise in serum level. Any patient predisposed to anphylaxis should wear identifying medical jewelry and avoid, whenever possible, drugs that could worsen an event or complicate its therapy. Unfortunately, most food-allergic children who experience severe throat, respiratory and cardiovascular symptoms of anaphylaxis do not receive epinephrine and many do not seek medical attention. For those who do seek medical care, their reported treatment is often suboptimal.
     Biphasic responses occur to anaphylaxis with significant frequency and therefore should be taken into consideration when one considers the observation period after the initial anaphylaxis event. An observation period of 8 hours is sufficient for most reactions, but since reactions can occur as long as 72 hours after resolution of the primary anaphylaxis event, a 24-hour observation period is a good option and the patient should be prescribed adrenaline auto-injectors. It is recommended that individuals who have experienced anaphylaxis should receive consultation from an allergist regarding diagnosis, prevention and treatment.

Treatment of mild symptoms
In case of a benign to moderate reaction, anti-histamine and steroid treatment are sufficient to control the process. Lying down with feet elevated is a good idea in order to pool the blood toward the heart away from the lower extremities. A severe reaction (hypotension, dyspnea) can be life threatening and adrenalin administration by the intramuscular route is indicated as discussed above.

Epinephrine Tablet?
2006 - It may be possible to administer epinephrine in a tablet -- placed under the tongue -- for the emergency treatment of anaphylaxis. Dr. Keith J. Simons from the University of Manitoba in Winnipeg and colleagues tested this approach in rabbits, which were given a new, rapidly disintegrating tablet containing epinephrine placed under the tongue. The oral treatment resulted in blood levels of epinephrine similar to those achieved with 0.3 mg epinephrine administered intramuscularly in the thigh -- the currently recommended emergency treatment for anaphylaxis. Tablets containing increasing doses of epinephrine were retained under the tongue for 5 minutes and the EpiPen was injected in the thigh. Blood was collected before dosing and at various times afterwards up to 180 minutes. The maximum blood concentrations and time to maximum blood concentrations were similar when epinephrine was given under the tongue or by EpiPen injection. The epinephrine tablets will be tested in humans.

Causes of Anaphylaxis
Drugs are the most common cause of anaphylaxis. Many drugs can cause anaphylaxis including antibiotics such as penicillin. Aspirin and the older nonsteroidal anti-inflammatory drugs (NSAIDs) that block cyclo-oxygenase-1 (COX-1) induce asthma attacks in patients with aspirin-exacerbated respiratory disease and urticaria in patients with chronic idiopathic urticaria. Weak inhibitors of COX-1, such as acetaminophen and salsalate, crossreact also but only with high doses of the drugs. Partial inhibitors of both COX-1 and COX-2, such as nimesulide and meloxicam, also cross-react but only at high drug doses. COX-2 inhibitors do not cross-react; however, all NSAIDs, including the selective COX-2 inhibitors, can sensitize patients and induce urticaria or anaphylaxis on next exposure to the drug.

Antibiotics cause it in 40 percent of the cases. The next most common allergy-inducing drugs are radiocontrast agents, which are used during diagnostic imaging tests, followed by chemotherapy medications to treat cancer.

Although food allergies have garnered a lot of attention lately, medications are actually the biggest cause of sudden deaths related to allergy. Nearly 60 percent of allergy-related deaths were caused by medications, while less than 7 percent were caused by food allergies.

More common in women?
J Allergy Clin Immunol. 2014 Dec 18. Estrogen increases the severity of anaphylaxis in female mice through enhanced endothelial nitric oxide synthase expression and nitric oxide production. Clinical observations suggest that anaphylaxis is more common in adult women compared with adult men,

Food Anaphylaxis
Food-related allergic reactions are the leading cause of anaphylactic reactions treated in the emergency department, accounting for approximately 30 000 emergency department visits each year, and 150-200 deaths. A number of foods can cause anaphylaxis including milk, eggs, peanut, and even sesame seed and macadamia nut.
   Peanut-allergic patients, particularly adolescents, need to be counseled on the risks of kissing someone who has recently eaten peanuts or peanut-containing products, even if that person brushed their teeth afterwards. There is a risk for allergens to be transferred in saliva.
   Some patients who are at risk for a severe allergic reaction caused by a food allergy may require two doses of epinephrine, rather than just one.

Allergol Int. 2015. A case of an anaphylactic reaction due to oats in granola.

Insect stings and Anaphylaxis
Most common cause of insect anaphylaxis is bee stings. Bites, stings and infestations can be fatal. Arthropod bites and stings are capable of inflicting injury, inciting allergic reactions, and transmitting systemic disease. Members of the Hymenoptera order are of particular importance because they are everywhere in nature, and their stings may cause life-threatening allergic reactions. Stings from bees, wasps, and ants produce a variety of manifestations. Anaphylaxis following an insect sting is the most serious complication. For individuals with a specific allergy to Hymenoptera venom, immunotherapy may be a relatively safe and effective treatment option. Patients should be referred to an allergist.

Anaphylaxis from Latex
Natural rubber latex is a resin sap produced in the cells of caoutchouc plants. It is a water dispersion of cis-1,4-polisopren (caoutchouc)--35%, stabilized with little amounts of proteins, sugar, alcohol, fatty acids and salts. The concentration of all solid substances is about 40%, the rest is water. Immunogenicity of latex depends on the proteins it contains. Cases of contact urticaria, asthma, rhinitis, and anaphylaxis after contacting with latex products has been widely reported by medical staff due to exposure to gloves and other latex products. A higher prevalence of latex allergy is connected to the fact of increased glove usage caused by the danger of virus infections: HIV, HBV, HCV. Latex allergy is one of the reasons of dramatic complications after surgical operations. People who are allergic to latex may have cross reactions to allergens not connected with occupational environment. These are: food and houseplants (Ficus benjamina). The frequency of latex allergy is about 0.1% of the general population. It can be as high as 1o% among medical staff and it reaches 50% among children with spina bifida.

Radiocontrast material
Allergy-like reactions may occur following administration of iodinated contrast media, mostly in at-risk patients (patients with history of previous reaction, history of allergy, co-treated with interleukin-2 or beta-blockers, etc.) but remain generally unpredictable. Severe and fatal reactions are rare events. All categories of contrast material may induce such reactions, although first generation (high osmolar contrast material) have been found to induce a higher rate of adverse events than low osmolar contrast material.

Vaccines

Beekeepers and Anaphylaxis management
Beekeepers and their family members are at an increased risk of severe sting anaphylaxis and therefore need especially careful instruction with regard to avoidance of re-exposure, emergency treatment and specific immunotherapy with bee venom.

Biochemical Mechanism of Anaphylaxis
Severe anaphylaxis is a systemic reaction affecting two or more organs or systems and is due to the release of active mediators from mast cells and basophils. A four-grade classification routinely places 'severe' anaphylaxis in grades 3 and 4 (death could be graded as grade 5).
     Studies with rodents indicate 2 pathways of systemic anaphylaxis: one mediated by IgE, Fc epsilonRI, mast cells, histamine, and platelet-activating factor (PAF), and the other mediated by IgG, Fc gammaRIII, macrophages, and PAF. The former pathway requires much less antibody and antigen than the latter. The IgE pathway is most likely responsible for most human anaphylaxis, which generally involves small amounts of antibody and antigen; similarities in the murine and human immune systems suggest that the IgG pathway might mediate disease in persons repeatedly exposed to large quantities of antigen. Gastrointestinal symptoms depend on serotonin and PAF; mediator dependence of systemic symptoms has not been determined. Both local and systemic anaphylaxis induced by ingested antigens might be blocked by IgA and IgG antibodies.