Peanut allergy
The rise in Peanut Allergy
Peanut, scientific name Arachis hypogeal, is a legume that is a common cause of food allergies. Peanut allergy can be potentially very dangerous, even life-threatening, particularly in adolescents and young adults and in people with asthma. It has become increasingly common over the past twenty years and is the most common food allergy in school-aged children.
It is possible for adults who were not allergic as children to develop an allergy to peanut. In these cases it is usually caused by oral allergy syndrome – a condition related to birch allergy – suffered by those with hayfever.
Peanut allergy is well-established in North America and the UK where 1% of children have peanut allergy, but it is much less common in other parts of the world. You might wonder why countries in Asia, where peanut is a major food source, do not have a high incidence of allergy to it. Research suggests that frying and boiling, the common method of cooking peanuts in Asia, makes the food less allergenic. Dry roasting, the common method of cooking peanuts in the United States, has been shown to make peanuts more allergenic.
The increase in peanut allergy has also been linked to the use of peanut protein in the oil used in cosmetics and skin creams (check labels for groundnut or arachis oil), exposure to peanut protein in breast milk or during pregnancy or to foods which cross-react, such as soy.
Can you outgrow Peanut Allergy?
For most people peanut allergy is a lifelong condition but if a RAST test (short for radioallergosorbent test) shows a level is less than 5 kU/L (kiliunits per litre) it would suggest that the allergy has been outgrown. People who outgrow their peanut allergy typically have milder reactions, smaller skin test reactions, and fewer allergies in general.
However, some people who have passed an oral food challenge to peanut become re-allergic to peanuts if they don’t eat peanuts enough after they have outgrown peanut allergy. So a person who has outgrown peanut allergy should continue to carry an Epi-pen for emergency use.
Other foods to watch out for if you have Peanut Allergy
Peanuts belong to the legume family, which also includes beans, peas and soy. While it is common for a person allergic to peanut to have positive allergy tests to other legumes, allergic reactions from eating these other legumes occurs in only 5% of people.
Lupin however, a legume commonly ground into flour and used in baked goods, should be avoided as those with peanut allergy can frequently experience allergic reactions to it. Check labels for lupin, lupine, lupinus.
People with peanut allergy may also be allergic to tree nuts such as almonds, cashews, walnuts and pecans. In fact, a recent study showed that about 1 in every 3 people (33%) with peanut allergy is also allergic to at least one tree nut. For this reason, as well as the fact that cross-contamination among tree nuts and peanuts is common it is recommended that people with peanut allergy avoid eating all nuts.
Treatment for Peanut Allergy
Anaphylaxis is the most dangerous symptom of peanut allergy and can be fatal. Someone experiencing anaphylaxis will have severe swelling of the face and throat that constricts the airway, making it impossible to breathe. They could also quickly experience shock, which if left untreated can be fatal.
The best therapy for peanut allergy is to avoid eating peanuts and to minimise exposure to them in skin creams. But since exposure to peanuts is frequently accidental, being prepared to treat the reaction with injectable epinephrine is paramount. Emergency medical care should always be sought if an allergic reaction to food occurs, whether or not epinephrine is used.
It’s also important to let friends, and school staff know how to administer epinephrine and the wearing of a medical alert bracelet or ID tag is recommended in case you are unable to communicate during a reaction.
Research into Peanut Allergy
There are various research studies ongoing looking at ways to treat and potentially cure peanut allergy. One well-documented peanut allergy treatment involves an anti-allergic antibody given by injection every 4 weeks. This increases the amount of peanut that can be tolerated without a reaction in people with peanut allergy.
Other studies for treatment of peanut allergy include sublingual immunotherapy, injection immunotherapy using isolated and engineered peanut proteins, and skin-prick and blood tests to check for antibodies.
The most accurate current test is a supervised oral food challenge, where patients are given small amounts of peanut in increasing doses to see if they react. But this can provoke such a strong reaction that some children have to stay in hospital whle it is being performed.
A safer and les traumatic new blood test has recently been developed by researchers at King's College London. This test identifies not only the presence of an allergy but how severe the allergic reaction will be. It measures the activity of white blood cells - basophils - which, when mixed with peanut, release chemicals such as histamine at levels that confirm the allergy.