How to Treat Penicillin Allergy

Penicillin Allergy

Penicillin Allergy

is an adverse auto immune response to any member of the antibiotic family derived from penicillum fungi. They belong to a group of antibiotics known as Beta Lactams. The molecular structure is also shared by other synthetically deduced penicillin variants (amoxicillin), cephalosporins and another group of antibiotics known as imipenem.

Penicillin and Cephalosporins are very important antibiotic drugs used against bacterial infection. It is primarily used in the treatment of diseases like syphilis and infections caused by staphylococci and streptococci. The different variants of the discussed drug belonging to the same family are penicillin G, procaine penicillin, benthazine penicillin and penicillin V.


A nationwide study revealed that more than half the population in America suffers from one or more allergies. The said allergy is the most common cause of drug induced asthma in the United States. Anywhere between 3 -10% of Americans suffer from this allergy. About 10% of the sufferers of this allergy continue to suffer from this allergy throughout their life.

What is the mechanism involved in Penicillin Allergy?

It is an immune mediated reaction of the body. The immune system reacts to the otherwise harmless drug and triggers the production of Immunoglobulin E (IgE) antibodies. These antibodies react with the proteins in the drug and causes the mast cells of the gut, skin and pharynx to produce the chemical histamine. Histamine causes the adverse reactions in the body by irritating nerve endings or dilating blood vessels causing swelling and inflammation.

Symptoms of allergy induced by penicillin

The symptoms can appear immediately after taking the antibiotic (within 72 hours) or can have a delayed impact(after 72 hours). The symptoms of the allergy are as follows:

  • Contact dermatitis, skin rash, urticaria, hives etc.
  • Angioedema or swelling of lips, tongue, eye lids , face etc.
  • Serum sickness (type III hypersensitivity to proteins in anti serum obtained from a foreign source).
  • Vasculitis or an inflammation of blood vessels. It is an auto immune disease.
  • Hemolytic anemia or the pre mature destruction of red blood cells (RBCs) in the blood vessels.
  • Asthma is also an immune mediated response of the said allergy.
  • Thrombocytopenia or a condition characterized by a significant drop in the platelet count in blood.
  • In an extreme situation, an emergency condition characterized by shortness of breath, confusion, head ache, drop in blood pressure and loss of consciousness can occur. This condition is known as Anaphylaxis.

Tests to detect the allergy

Reactions to the allergen concerned in this case is best detected by skin testing. Skin prick tests ( the allergen is introduced into the skin through pricks made on the skin) or patch testing ( the allergen is introduced into the body by applying patches containing it especially on the back) are popularly used. A commercially available extract containing the said allergen is available for skin testing. The extract is called Pre-Pen. Skin testing helps to determine the presence or absence of the IgE antibodies.

Blood tests, RAST or Radioallergosorbent test or an enzyme linked immunosorbent assay (ELISA) can detect IgE antibodies to the main penicillin determinant. The individual may be allergic to the other variants which has the same chemical structure as penicillin. Hence a negative RAST test can never rule out the said allergy.

How to treat Penicillin allergy?

  • Immediately stop the use of any penicillin related antibiotic. People allergic to penicillin can exhibit severe reactions to cephalosporins. It would be a good idea to eliminate the use of cephalosporins also.
  • An alternate antibiotic needs to be prescribed.
  • Antihistamines can be used to combat the excess histamine in the body. They bring immediate relief from symptoms. Over the counter antihistamines like Claritin, Zyrtec, Benadryl , Allegra can help.
  • Immunosuppresant corticosteroids can help by reducing inflammation. Deltasone and Prednisone can improve symptoms of asthma and breathing difficulties by reducing the inflammation of airways.
  • In case of anaphylaxis, an emergency dose of epinephrine needs to be administered to prevent it from progressing into a life threatening condition.
  • Penicillin Desensitization is also used under medical supervision. This process involves giving small doses of the antibiotic to the allergic individual. This works by making the mast cells unresponsive to the specific antigen. The immunological tolerance is gradually increased till the person is able to tolerate the recommended dose.
  • Self medication in this allergy can be complicated. Cross sensitivity to different drugs are possible and one needs to be careful before popping any random over the counter pill. Medical supervision is of utmost importance in this case.

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