Allergies occur when your immune system reacts to a foreign substance that doesn’t cause a reaction in most people. Your immune system produces substances known as antibodies. When you have allergies, your immune system makes antibodies that identify a particular allergen as harmful, even though it isn’t. When you come into contact with the allergen, your immune system’s reaction can inflame your skin, sinuses, airways, or digestive system.
The severity of allergies varies from person to person and can range from minor irritation to anaphylaxis — a potentially life-threatening emergency. While most allergies can’t be cured, treatments can help relieve your allergy symptoms.
What causes allergy?
Researchers aren’t exactly sure why the immune system causes an allergic reaction when a normally harmless foreign substance enters the body. Allergies have a genetic component. This means parents can pass them down to their children. However, only a general susceptibility to an allergic reaction is genetic. Specific allergies aren’t passed down. For instance, if your mother is allergic to shellfish, it doesn’t necessarily mean that you’ll be, too.
Common types of drug allergens include Penicillin, sulfa drugs, and herbal medications which contain common triggers.
What is penicillin allergy?
A penicillin allergy is an allergic reaction that occurs when your body’s immune system overreacts to the penicillin antibiotic. True penicillin allergy is rare with the estimated frequency of anaphylaxis at 1-5 per 10 000 cases of penicillin therapy. Hypersensitivity is, however, its most important adverse reaction.
What are the symptoms of penicillin allergy?
Common allergic reactions to penicillin include rashes, hives, itchy eyes, and swollen lips, tongue, or face. In rare cases, an allergy to penicillin can cause an anaphylactic reaction, which can be deadly. This type of reaction usually happens within an hour after you take penicillin. Symptoms include:
- Difficulty breathing
- Hives, wheezing
- Loss of consciousness
- Rapid or weak pulse
- Skin turning blue
If you think you are having an anaphylactic reaction, inject epinephrine in your thigh muscle and then call 911 immediately.
What makes you more likely to have a severe allergic reaction to penicillin?
Severe allergic reactions to penicillin can be dangerous and life-threatening. You may be more likely to have this type of reaction if you have had:
• A positive skin test for penicillin allergy.
• Hives that appeared quickly after you took the penicillin.
• A previous anaphylactic reaction to penicillin.
If any of these apply to you, you should receive another antibiotic or undergo desensitization therapy. In this type of therapy, under your doctor’s supervision, you start taking small amounts of penicillin and gradually increase how much you take. This lets your immune system “get used to” the medicine, and you may no longer have an allergic reaction. Desensitization may have to be repeated if you have to use the antibiotic again in the future (desensitization doesn’t last long).
You are not likely to have an anaphylactic reaction to penicillin if you have had a rash that looks like measles that appeared from a few hours to days after you took penicillin.
What Antibiotics Can You Not Take If Allergic To Penicillin?
All antibiotics in the penicillin class should be avoided if you are allergic to Penicillin, these drugs include:
- Penicillin V
- Penicillin G (Pfizerpen, Permapen)
- Amoxicillin (Amoxil)
- Amoxicillin/clavulanate (Augmentin)
- Ampicillin (Unasyn)
- Nafcillin (Nallpen)
- Oxacillin (Bactocill)
- Dicloxacillin (Dycill, Dynapen are discontinued brands in the US; generic is available)
- Cloxacillin (discontinued in the US)
- Piperacillin (Pipracil)
- Piperacillin/tazobactam (Zosyn)
- Ticarcillin (Ticar) (Discontinued in the US; ; generic is not available))
- Ticarcillin/clavulonate (Timentin) (Discontinued in the US and a generic is not available.)
- Carbenicillin (Geocillin)
- Flucloxacillin (Floxapen)
- Hetacillin (Natacillin)
- Mezlocillin (Mezlin)
How is an allergic reaction to penicillin treated?
If you use penicillin and then get hives and have trouble breathing or have other symptoms of anaphylaxis, call 911 or other emergency services immediately. For emergency treatment, people typically get an epinephrine shot. If symptoms do not go away, you may need more shots. You may also have antihistamines and corticosteroids put directly into a vein (intravenously).
If you have a mild allergic reaction, you may control your symptoms with antihistamines that you can buy without a prescription. But you may need prescription medicine if those over-the-counter medicines don’t help or if they cause bothersome side effects, such as drowsiness. If you have had a previous serious reaction to penicillin, you should carry and know how to use an epinephrine shot. Let your doctor know about any medicine reaction right away.