E.O. is an 8-year-old girl with a history of asthma and allergy to bee stings. She has been brought to the clinic complaining of a throat infection. Her health care provider prescribes a course of penicillin to manage her current infection and cautions her parents to watch her closely for a reaction.

Discussion Questions 1. What type of reaction is the health care provider concerned about and why? The type of reaction that the health care provider is concerned about is an allergic reaction to the penicillin. Since E.O is already allergic to bee stings and has a history of asthma, which are both Type I hypersensitivities, it is very likely that E.O could have an allergic reaction to the penicillin. Since penicillin is found in cow milk and the patient could have been exposed to it through milk, breast milk, or in utero, E.O could become sensitized to it. If E.O is further exposed to the allergen (being that her health care provider prescribed her penicillin), there could be an allergic reaction to it. Exposure to penicillin can result in the degranulation in mast cells and the release of histamine, which could cause the reaction, which is even more likely since E.O has two Type I hypersensitivities. 2. Explain the role of IgE and mast cells in type I hypersensitivity reactions. Why might E.O. react adversely to the antibiotic with the first use? During sensitization, IgE antibodies bind to the surface of mast cells, which makes the mast cells “sensitized.” When someone is exposed again to the same allergen, which results in the degranulation of mast cells and the release of histamine. Histamine will cause rapid constriction of E.O’s blood vessels causing a hypersensitive