Summary: The severity of allergic reactions can range from mild to life threatening. Understanding the different types of reactions is necessary to understand when to seek emergency care. Reactions limited to a small spot on the skin are minor. Hives (urticaria) can be treated with diphenhydramine (antihistamine) at home. Reactions that result in difficulty breathing or throat tightness require prompt medical attention. Symptoms of weakness, pale color, drowsiness or passing out (loss of consciousness) may be due to the most severe type of allergic reaction which requires emergency attention; call 911.
The severity of allergic reactions can range from mild to life threatening. Understanding the different types of reactions is necessary to understand how to treat these and when to seek emergency care. Reactions can be classified several ways, but it would be more useful for most of us to group allergic reactions into 4 types based on the parts of the body that are affected. These types include 1) local reactions, 2) urticaria (hives), 3) breathing difficulty (respiratory), 4) poor blood circulation (shock).
1) Local reactions include mosquito bites, ant bites and contact allergies such as a rash from plant sap. These are usually itchy and red. Some contact allergies only affect sensitive individuals. Common substances include rubber, leather, plant saps, hair dye and nickel (stainless steel and costume jewelry), but allergy to anything is possible. Local reactions are limited to the area of contact, where the bite or contact occurred. If the reaction spreads to other parts of the body, then this is no longer a local reaction. Local reactions are generally not serious. They are easily treated with hydrocortisone cream applied topically (rubbed onto the skin) which can be purchased without a prescription. The local reaction represents inflammation. Corticosteroids (such as hydrocortisone, triamcinalone, betamethasone, etc.) are anti-inflammatory. Prescription corticosteroids are usually stronger. Take a small amount of this cream and rub it in well. This will make it less inflamed and thus, less itchy.
Some local reactions can occur in the eye. While these are usually not serious, it would be difficult to describe all the possibilities in a brief paragraph. The eyes are very important, therefore, I would suggest seeing a physician right away if the eyes are involved.
Sometimes, large local reactions result, usually from toxic venoms such as bees, centipedes, scorpions and jellyfish. When a single lesion is large (such as in a centipede bite) or there are multiple lesions (such as with jellyfish or fire ants), these may be best treated with topical steroid creams plus the same type of anti-allergy medications used for the more serious types of allergic reactions described below. If the reaction is severe, see a physician.
2) Urticaria, more commonly known as hives, looks like large mosquito bites. They are pink, puffy (elevated above the skin) and itchy. Hives, resulting from the release of histamine (a chemical that causes allergic reactions), usually occur on many parts of the body at the same time. Urticaria can often result in severe swelling over large areas of the body. This rapid and severe spread is very impressive and is often thought to be an emergency. Urticaria may occur together with some findings similar to local reactions such as eye swelling. As long as the allergic reaction is limited to the skin, urticaria is usually not an emergency. Urticaria can be treated with antihistamines (drugs that reverse histamine reactions) such as diphenhydramine (available without a prescription at any drug store and at most supermarkets). If given early, a single dose of diphenhydramine is often sufficient to reverse the reaction and the hives will resolve.
Some hives are not urticaria. Erythema multiforme (EM for short) is a type of hives that does not respond well to medication treatment of any type. EM looks slightly different than hives, but this difference is subtle so only experienced physicians can recognize EM easily. EM resolves on its own, but it often takes about two weeks. Even potent anti-allergy medications do not seem to cure EM any faster. EM may be associated with minor complications such as joint swelling, but since serious complications can occur with severe forms of EM, it should be evaluated by your physician.
Hives can occur with more serious allergic reaction types (breathing difficulty and/or shock) and in such cases, victims will have the symptoms of respiratory difficulty and/or shock (described below). If the allergic reaction is limited only to the skin, this is usually not serious, but spread to the eyes or mouth could suggest a serious reaction and these should be evaluated by a physician.
3) Breathing difficulty (respiratory) symptoms result when the airways (the tubes that enter the lungs) become swollen and narrow. Noisy breathing, wheezing, difficulty breathing, chest tightness, throat tightness or a hoarse voice could result. These symptoms often occur suddenly, often together with hives, after being exposed to an allergic substance such as bee stings or allergic foods. This type of reaction is more serious so an evaluation and treatment by a physician is immediately required. If the breathing difficulty is severe, 911 should be called. If it is not severe, then take your child to see a physician immediately. Treatment for this type of reaction depends on its severity. It often includes a bronchodilator (a medication to open the airways such as albuterol), an antihistamine (such as diphenhydramine) and corticosteroids (an anti-inflammation drug such as prednisone). Antihistamines and corticosteroids suppress different arms of the allergic reaction. Epinephrine (explained below) is often given as a small injection under the skin since this drug opens the airways and it also raises the blood pressure just in case the allergic reaction is about to progress to shock (described below).
4) Shock. Reactions which result in poor circulation are rare, but this is the most serious type of allergic reaction. Medically, "shock" means that the circulation is not delivering blood adequately to the important parts of the body. The term "anaphylaxis" is used to describe an exaggerated allergic reaction. "Anaphylactic shock" is the term used to describe this most severe type of allergic reaction. In anaphylactic shock, the blood vessels suddenly open up and the amount of blood circulating through the vessels becomes inadequate. Think of the blood vessels like a set of pipes filled with water. If the pipes suddenly become larger and the amount of water stays the same, the pipes are no longer full and more water must be added to fill them. It's similar to losing a lot of blood very quickly. The blood pressure drops and the amount of blood circulating to important parts of the body (such as the brain, heart and kidneys) suddenly drops. In severe anaphylactic shock, the victim will pass out due to inadequate blood circulation to the brain. Lying down is somewhat protective to the body since blood does not need to be pumped up hill when the victim is lying down so it preserves at least some blood flow to the brain improving the victim's chance of recovery. However, without rapid and proper treatment, anaphylactic shock can soon result in death.
In mild or early anaphylactic shock, the victim will feel weak or lightheaded because blood flow to the brain is diminished. Sitting or lying down may temporarily relieve the lightheadedness, but things may rapidly worsen if treatment is not started.
Anaphylactic shock should be treated immediately with epinephrine (also known as adrenaline), intravenous fluids and other anti-allergy medications. IV fluids fill the enlarged blood vessels to help restore blood pressure. Epinephrine causes the enlarged blood vessels to constrict and return back to their normal size to improve circulation to the vital organs. Epinephrine given intravenously has immediate and very potent effects. Just to give you an idea of how strong this drug is, it is usually used to help restart the heart in a cardiac arrest. The only time epinephrine is used intravenously is in a dying patient with a failing heart, cardiac arrest and anaphylactic shock. Other anti-allergy medications (antihistamines and corticosteroids) are needed to slowly stop the progress of the allergic reaction, but without immediate epinephrine, death may result before these other medications can help. Thus, when anaphylactic shock is suspected, 911 should be called so that paramedics can immediately recognize the anaphylactic shock, start an IV and begin epinephrine.
Epinephrine can be given into the muscle as an injection, but it might not be absorbed into the circulation fast enough to reverse anaphylactic shock that is progressing rapidly, in which case, IV (intravenous) epinephrine is necessary. Epinephrine can also be given subcutaneously; as a small injection under the skin (not into the muscle). This type of small epinephrine dose is slower, therefore it is safer, but it is only used if the degree of shock is minimal. Epinephrine also open the airways so it is very useful if there is difficulty breathing due to narrowing of the tubes in the lungs.
Many patients with a previous episode of a severe allergic reaction, have an epinephrine pen injector prescribed to them. When an allergic reaction occurs, they are instructed to push this pen against their thigh, which causes the spring to inject the epinephrine into the thigh muscle. While this sounds like a good idea, there are two problems with this. Since severe allergic reactions are infrequent and unpredictable, often occurring suddenly and unexpectedly, most patients are not carrying the epinephrine pen injector with them when they need it. Also, if anaphylactic shock is severe, a single epinephrine shot is not sufficient to fully stop the allergic reaction.
Anaphylactic shock is the most severe type of allergic reaction. This is potentially deadly and immediate medical attention is required. 911 should be called so that treatment can be started immediately before arrival at the hospital. Anaphylactic shock should be suspected if allergic reaction symptoms such as rapid onset of hives, swelling or difficulty breathing occur together with passing out, looking pale or feeling faint, weak and lightheaded when standing. The onset of these symptoms can be very rapid often following a bee sting or exposure to allergic foods. Call 911 for this.