What Is a Penicillin Allergy?

Penicillin belongs to the -lactam family of antibiotics, and its efficacy is significant and widely used. However, penicillin easily causes adverse drug reactions. 1% to 10% of the population are allergic to penicillin. Allergic reactions can occur at any age, dosage form, dosage and route of administration. Severe anaphylactic shock can be life-threatening.

Basic Information

Visiting department

Allergy, Dermatology

Multiple groups

Allergic

Common symptoms

Urticaria, angioedema, pruritus, allergic rhinitis, asthma and edema of the throat, etc.

Contagious

no

Causes of penicillin allergy

Penicillin is a hapten that enters the body and combines with tissue proteins to form a full antigen. For patients with allergies, the whole antigen formed after penicillin enters the body can cause lymphocytes to produce specific antibodies lgE. LgE can adhere to the nasal, pharynx, vocal cord, and bronchial mucosa, making the body allergic. When the patient takes oral or injection again, or even topical penicillin, the new antigen is combined with the specific antibody lgE and causes a type allergic reaction. A large amount of histamine, bradykinin and other sensitization occur in the patient's blood. Substances, acting on effector organs, cause capillary dilatation and increased permeability, vascular smooth muscle relaxation, and vascular bed volume increase, and various symptoms occur immediately.

Clinical manifestations of penicillin allergy

Allergic reactions caused by penicillin are also classified as type 4. Type I reaction, also known as immediate response, is related to the specific IgE of penicillin degradation products. It manifests as allergies, urticaria, angioedema, itching of the skin, allergic rhinitis, asthma, and laryngeal edema. Among them, anaphylactic shock is the most serious, and sometimes patients can quickly occur with a small amount of skin test fluid, and the mortality rate is 10% to 20%.

Type response is mediated by specific IgG and IgM. Hemolytic anemia can occur after using large doses of penicillin. Type reactions are related to BPO-specific antibodies. Serum disease-like syndromes that appear in the treatment of penicillin (especially long-acting penicillin) are manifested as urticaria or other types of rash, fever, joint pain, and systemic lymphadenopathy. Type reaction is manifested as contact dermatitis (it is no longer topical and is rare now). The mechanism of adverse drug reactions caused by ampicillin is non-allergic, manifested as eruptive drug rash, with an incidence of about 10%.

Penicillin allergy test

Before using various penicillins, patients should be asked if they have ever used penicillin and have a history of allergies to penicillin. Allergy tests should be performed before use. The drug can be used only if the test results are negative. There may be false positives and false negatives in skin test results.

The skin test solution currently used in China is directly prepared from penicillin. Foreign countries have degradation products skin test solution (penicillium thiazole polylysine, PPL).

At present, there is no standard reagent for in vitro tests to detect penicillin allergy in China.

Penicillin Allergy Diagnosis

History of penicillin injection. Mild people have nausea, itching, rash, asthma, chest tightness, shortness of breath, etc. In severe cases, pale, cold sweats, cyanosis, weak pulses, irritability, edema of the throat, difficulty breathing, decreased blood pressure, consciousness Shock symptoms such as loss, convulsions, and incontinence.

Penicillin Allergy Treatment

After an allergic reaction to a drug occurs, first of all, it is necessary to quickly determine the possible allergenic drug and quickly block the patient's continued exposure to the allergic drug. Patients who have been identified as being allergic to penicillin should not be given a penicillin skin test again. Should be treated promptly. During treatment and after recovery, attention should be paid to polyvalent allergy and cross-allergy.

Rescue of anaphylactic shock: The patient lies on his back, monitors vital signs (blood pressure, etc.), maintains fluid channels, and inhales oxygen. First try to increase blood pressure (immediately give 0.5 to 1 mg of adrenaline, and re-administer if necessary; booster drugs can be given as needed.); Throat edema, should first resolve dyspnea or suffocation. According to the needs of the condition, appropriate amounts of corticosteroids, antihistamines, acid correction and other drugs are given for treatment.

Treatment of mild cases: such as itching of the skin, unilateral urticaria or angioedema, mild eruptive drug rash, etc., oral antihistamines can be given, and small doses of corticosteroids and other drugs can be used for treatment if necessary.

Treatment of severe cases: such as exfoliative dermatitis, toxic epidermal necrolysis, severe erythema polymorpha, etc., combined with visceral damage, complicated conditions, severe cases, must be actively and comprehensively rescued. During salvage, attention should be paid to internal organ function, water and electrolyte balance, supportive therapy, and infection prevention. According to the needs of the disease, drugs such as corticosteroids, immunoglobulins, and immunosuppressants can be given for treatment.