Allergy (Allergies)

  • Medical Author:
    Allison Ramsey, MD

    Dr. Allison Ramsey earned her undergraduate degree at Colgate University and her medical degree at the University of Rochester School of Medicine and Dentistry. She completed her internal medicine training at the University of Rochester School of Medicine and Dentistry and remained at the university to complete her fellowship training in allergy and clinical immunology. Dr. Ramsey is board certified in internal medicine and allergy and immunology. Her professional interests include the treatment of drug allergy and eosinophilic disorders. She also enjoys teaching medical trainees. She is a member of the American Academy of Allergy, Asthma, and Immunology, the American College of Allergy, Asthma, and Immunology, the New York State Allergy Society, and the Finger Lakes Allergy Society. In her personal life, her interests include exercise, especially running and horseback riding; and spending time with her husband and two children.

  • Coauthor: Syed Shahzad Mustafa, MD
    Syed Shahzad Mustafa, MD

    After growing up in the Rochester area, Dr. Mustafa pursued his undergraduate studies at the Johns Hopkins University in Baltimore and attended medical school at SUNY Buffalo. He then completed his internal medicine training at the University of Colorado and stayed in Denver to complete his fellowship training in allergy and clinical immunology at the University of Colorado, National Jewish Health, and Children's Hospital of Denver.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Quick GuideAllergy: What Happens in a Nasal Allergy Attack

Allergy: What Happens in a Nasal Allergy Attack

What causes allergies? (Continued)

In the pet cat example, the dad and the youngest daughter developed IgE antibodies in large amounts that were targeted against the cat allergen. The dad and daughter are now sensitized or prone to develop allergic reactions on repeated exposures to cat allergen. Typically, there is a period of "sensitization" ranging from days to years prior to an allergic response. Although it might occasionally appear that an allergic reaction has occurred on the first exposure to the allergen, there needs to be prior exposure in order for the immune system to react. It is important to realize that it is impossible to be allergic to something that an individual has truly never been exposed to before, though the first exposure may be subtle or unknown. The first exposure can even occur in a baby in the womb, through breast milk, or through the skin.

IgE is an antibody that all of us have in small amounts. Allergic individuals, however, generally produce IgE in larger quantities. Historically, this antibody was important in protecting us from parasites. In the example above, during a sensitization period, cat dander IgE is overproduced and coats other cells involved in the allergic response, such as mast cells and basophils, which contain various mediators, such as histamine. These cells are capable of leading to an allergic reaction on subsequent exposures to the cat allergen (cat dander). The cat protein is recognized by the IgE, leading to activation of the cells, which leads to the release of the allergic mediators mentioned above. These chemicals cause typical allergic symptoms, such as localized swelling, inflammation, itching, and mucus production. Once primed, or sensitized, the immune system is capable of mounting this exaggerated response with subsequent exposures to the allergen.

On exposure to cat dander, whereas the dad and daughter produce IgE, the mom and the other two children produce other classes of antibodies, which do not cause allergic reactions. In these nonallergic members of the family, the cat protein is eliminated uneventfully by the immune system and the cat has no effect on them.

Another part of the immune system, the T-cell, may be involved in allergic responses in the skin, as occurs from the oils of plants, such as poison ivy, poison oak, poison sumac, or reactions to metal, such as nickel. The T-cell may recognize a certain allergen in a substance contacting the skin and cause an inflammatory response. This inflammatory response can cause itching, rash, and discomfort. Continue Reading

Reviewed on 4/18/2016
References
REFERENCES:

Fiocchi A, Assa'ad A, Bahna S; Adverse Reactions to Foods Committee; American College of Allergy, Asthma and Immunology. Food allergy and the introduction of solid foods to infants: a consensus document. Adverse Reactions to Foods Committee, American College of Allergy, Asthma and Immunology. Ann Allergy Asthma Immunol. 2006 Jul;97(1):10-20; quiz 21, 77.

Price D, Bond C, Bouchard J, Costa R, Keenan J, Levy ML, Orru M, Ryan D, Walker S, Watson M. International Primary Care Respiratory Group (IPCRG) Guidelines: management of allergic rhinitis. Prim Care Respir J. 2006 Feb;15(1):58-70. Epub 2005 Dec 27.

American College of Allergy, Asthma, & Immunology. Food allergy: a practice parameter. Ann Allergy Asthma Immunol. 2006 Mar;96(3 Suppl 2):S1-68. No abstract available.

Flinterman AE, Pasmans SG, Hoekstra MO, Meijer Y, van Hoffen E, Knol EF, Hefle SL, Bruijnzeel-Koomen CA, Knulst AC. Determination of no-observed-adverse-effect levels and eliciting doses in a representative group of peanut-sensitized children. J Allergy Clin Immunol. 2006 Feb;117(2):448-54.

Scibilia J, Pastorello EA, Zisa G, Ottolenghi A, Bindslev-Jensen C, Pravettoni V, Scovena E, Robino A, Ortolani C. Wheat allergy: a double-blind, placebo-controlled study in adults. J Allergy Clin Immunol. 2006 Feb;117(2):433-9.

Medically Reviewed By: Ellen Reich, MD, Board Certified in Allergy and Immunology, Board Certified in Pediatrics and Michael Manning, MD, of the American Board of Allergy and Immunology.

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