There are many agents used in anaesthetic practice which can cause allergic reactions:

• Antibiotics: The risk of penicillin fatal allergy is about 1 in 75,000. About 15% of patients have a history of penicillin allergy. Cephalosporins have a similar structure to penicillins, and 10% of patients who have a history of penicillin allergy also have an allergy to cephalosporins (eg.cefuroxime; Keflex etc). Vancomycin and sulphonamides can also cause allergic reactions.
• Muscle Relaxants: Allergic reactions are possible with relaxants that cause histamine release e.g. curare, suxamethomium, atracurium, mivacurium.
• Local Anaesthetics: True allergic reactions to local anaesthetics are very rare. If they occur, they are to agents in the ester group (i.e.procaine, amethocaine) rather than the amide group (lignocaine and bupivacaine).
• Analgesics: Aspirin and other non steroidal anti-inflammatory drugs (NSAIDs): reactions to aspirin and NSAIDS are usually skin manifestations (urticaria, oedema) or respiratory system (bronchospasm, rhinitis, sinusitis). Aspirin induced wheezing is rare in non-asthmatics, but occurs in 10% of asthmatics, 35% of asthmatics with a history of nasal polyps and allergic rhinitis, and 75% in asthmatics who give a history of aspirin induced reactions. Narcotics: (eg. Morphine, pethidine, codeine): cause histamine release and usually skin allergic reactions.
• Contrast Media: Incidence of reactions to contrast media (eg.iodine) is about 7%. Reactions include nausea, vomiting, flushing urticaria, wheezing, low blood pressure.
• Others:
  Insulin preperations: Allergic reactions to insulin are usually skin manifestations, which usually disappear with repeated treatment, because of immunity. Severe reactions to insulin are very rare. Colloid Solutions. (Incidence: 0.033%) Colloids are fluids given as a drip (via a vein). They remain in the blood circulation for many hours, and are therefore very useful in patients where severe blood loss is a problem. Many of these preperations are starch or gelatin derivatives, and very rarely can cause severe allergy. (e.g. gelofusin; haessteril; dextrans, mannitol).
  Latex: Latex is a rubber material found in a wide variety of surgical equipment, such as urinary catheters, surgical gloves, rubber tips of syringes, some adhesives etc. Mild allergic reactions to latex are skin rashes, itching etc. Severe cases can cause asthma like attacks (bronchospasm) and low blood pressure and severe shock. Latex allergy is present in about 1% of the general public, 10% of health workers, and as high as 67% in patients with spina bifida (owing to repeated passage of urinary catheters).

Clinical Features:

Symptoms of allergic reactions include:

• Skin reactions: rashes, urticaria, itching swelling.
• Respiratory: shortness of breath; wheezing; cough; bronchospasm (constricted air passages); pulmonary oedema (water in the lung).
• Cardiovascular: Feeling faint; low blood pressure; collapse.
• Gastrointestinal: Nausea, vomiting, diarrhoea, abdominal pains.
• Management: The most important measure in severe cases is the administration of adrenaline, as it elevates the blood pressure and relieves constriction of the air passages. Other useful agents include antihistamines which reduce the release of the offending histamine, and steroid drugs. When the patient is clinically stable; repeated blood samples over a 24 hour period are taken, and skin tests to identify the offending agent. The patient should then wear a bracelet or some form of hazard alert.