What Is Sesame Allergy

Sesame allergy is a term that refers to a reaction that can happen in some people when their bodies come into contact with sesame seeds or extracts from sesame seeds.

First identified in the 1950s, the incidence of allergy to sesame seeds is on the rise, most likely due to the increased use of sesame seeds in food production. Allergy to sesame is now one of the top 10 allergies in the UK and the most common seed allergy.¹

Sesame seeds come from the sesame plant, which has been cultivated as a source of food for thousands of years. The seeds can be used whole in foods such as Tahini, Hummus, and Halva, or cold-pressed to produce sesame oil which has a wide range of uses in cooking, cosmetic manufacture, and pharmaceutical manufacture.² Some people with a mild allergy to sesame will be able to eat foods containing the whole seed, as the part of the sesame seed that causes the allergic reaction (known as the antigen or allergen) is inside the seed's shell and only released when the seed is crushed. 

What is an allergic reaction?

Allergic reactions happen when the body’s immune system wrongly identifies a substance as a threat. The body then mounts an immune response against the substance, which results in a range of symptoms. In mild cases, this can be limited to symptoms like an upset stomach or a rash, but in severe cases, the reaction can lead to a condition called anaphylaxis, which can be fatal if not treated immediately.³ People with one type of allergy are often prone to developing others, a state which is termed atopy. Atopic people will often have conditions such as eczema, asthma, or allergies to substances other than sesame.⁶

Types of reaction

Anaphylaxis

An anaphylactic reaction to sesame occurs immediately after coming into contact with or ingesting sesame products. In these reactions, a chemical produced by the body's immune system called IgE recognizes the allergen molecule of the sesame seed and stimulates the body to produce chemicals that cause a widespread reaction which results in a range of symptoms, including swelling of the lips, tongue, and airway, wheezing, rash, urticaria (hives), itching, abdominal pain, diarrhea and vomiting.³ If left untreated the reaction affects all organs in the body and results in anaphylactic shock Anaphylaxis - NHS (www.nhs.uk). Anaphylaxis requires immediate medical treatment with adrenaline and steroids to dampen down the immune response and control the symptoms.⁵ A person who has had an anaphylactic reaction will often be provided with their medication in a device called an EpiPen. This is a pen-shaped device containing an injectable adrenaline mix that can be used in the event of future anaphylactic reactions. 

Delayed allergic reactions

In some people, physical contact with sesame seed or sesame oil within cosmetic products or oils will result in an allergic reaction that develops after several hours. This type of reaction is a result of cells from the immune system, called T-cells, reacting to the antigen in sesame and causing a localized reaction at the point of contact. This results in skin irritation and redness, termed contact dermatitis.⁴

Diagnosing sesame allergy.

Why is diagnosis important?

If a person develops any symptoms of allergy it is important to find out what the substance was that provoked the body into developing an allergic reaction. This will help the person to avoid further allergic reactions by avoiding the substance. It is important to know the cause of allergy, even in people who have had a mild reaction, as future exposure to the same substance could result in a more severe reaction.

To correctly diagnose the cause of an allergy, a person will be referred to a specialist in allergy medicine who can arrange appropriate tests to find out the cause of their allergy and help to prevent them from having any future allergic reactions by advising them on what substances they should avoid. 

What will a doctor want to know?

If someone has suffered from a reaction that is thought to be the result of an allergy, a doctor will take a detailed history of the event, including details of any foods consumed before the reaction occurred, the symptoms that the person experienced, any previous history of allergies or immune-mediated illnesses such as asthma or eczema and any family history of allergies or immune-mediated illnesses.⁷

What tests can be performed to test for allergy?

Specialist tests can be carried out to test for the substance which resulted in an allergic reaction occurring. These include:

Skin-prick testing

Skin prick testing involved placing a small drop of a solution made up of suspected allergens onto the skin of the inner arm and then using a small needle to make a prick in the skin, pushing a tiny amount of the allergen through the surface of the skin. The reaction to each allergen tested is assessed by the degree of any redness and swelling that occurs at the skin-prick test site. Skin prick testing is not strongly supported for diagnosis of sesame allergy, as there is a high degree of false positives due to a similarity between the allergens found in sesame seeds and peanuts.⁸

Blood tests

Blood tests for sesame allergy will look for the IgE antibody which is specific for the sesame allergen. This test can result in false positives due to the similarities between peanut and sesame allergens. 

Food challenges

In some cases, where skin-prick testing and blood tests have not helped determine the cause of an allergic reaction, a food challenge test may be performed. This test is carried out in a hospital setting with all the treatments required to manage an anaphylactic reaction on standby in case the patient develops a severe reaction. The patient is given a tiny amount of the substance suspected of being the cause of their allergy, and they are monitored for signs of allergic reaction. This is considered the gold-standard test for diagnosing sesame allergy.⁸

Managing sesame allergy

Preventing allergic reactions

Sadly, an allergy to sesame cannot be cured. However, it is possible to prevent allergic reactions by avoiding any exposure to sesame seeds or sesame oil. All packaged food includes a list of ingredients on the packaging. As sesame is one of the top 14 causes of food allergy in the UK, foods containing it must, by law, be highlighted in bold in the ingredients lists of foods. Catering businesses are also legally required to highlight sesame as an ingredient in any foods they are serving. Individuals with sesame allergy are encouraged to carefully read the ingredients of any foods before consuming them. This can seem like a daunting task! Patients with sesame allergy may be referred to a dietician to help them manage their diet safely. 

Treating an allergic reaction

If someone with a sesame allergy develops any signs of an allergic response, they should start treatment immediately. In mild cases, an antihistamine tablet can help manage symptoms. If there are any concerns that the patient is developing an anaphylactic reaction they should be given intramuscular adrenaline. People who are known to have an allergy that results in an anaphylactic response will be provided with an Adrenaline Auto-Injector (also known as an EpiPen) which can be used to give an immediate dose of adrenaline to help control the symptoms. Whilst this is given, an ambulance should be called, and the patient should be taken to an emergency department for ongoing treatment. 

Summary

Allergy to Sesame is common, being recognized as one of the top 10 causes of food allergy in the UK. If you have developed any symptoms that are consistent with an allergic response, you should be seen by a doctor for investigation and advice on how to manage your condition. The primary management will be to avoid any foods, cosmetics, or pharmaceutical products which contain sesame. Whilst this may seem daunting to consider, there are many sources of support, including Allergy UK | National Charity, Anaphylaxis UK | Supporting people with serious allergies | Anaphylaxis UK, and NHS websites on Allergies - NHS (www.nhs.uk), Food allergy - NHS (www.nhs.uk) and Anaphylaxis - NHS (www.nhs.uk).

Sarah Morwood

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