What properties does sesame have?
Sesame is one of the seed crops cultivated in many regions of the world and has been known since prehistoric times. Its main producer is India, which exports sesame in large quantities to, among others, Europe. It comes in several varieties – most commonly white or black. The demand for sesame is due to the popularity of African, Asian and Indian cuisine as well as its high nutritional value. The oily seeds are a superb source of unsaturated fatty acids [1]. They also contain proteins (20%) and vitamins or trace elements, e.g. iron, phosphorus, calcium, potassium [1].
However, sesame is a strong allergen, dangerous also because of the risk of accidental contact with products that may be contaminated with it. It is a key ingredient in halva, sesame seeds and tahini paste added to hummus. It can hide in processed foods such as bakery products and cereals [1]. Furthemore, it is also found in pharmaceuticals and cosmetics. Sesame seeds in EU countries – according to current legislation – should be labelled as allergenic ingredients on food labels [1].
Sesame – cross reactions and allergens
Sesame’s main allergen is Ses i 1, which does not reduce allergenicity when exposed to heat and is resistant to digestive enzymes. It can cause severe allergic reactions [1,2]. Ses i 1 accounts for 15 to 25% of all proteins found in sesame. Other allergens of major clinical importance are: Ses i 3, Ses i 4, Ses i 5, Ses i 6, Ses i 7 [2]. Ses i 6 is the most abundant protein (60-70%) [1].
Sesame exhibits high cross-reactivity, e.g.:
- Ses i 1 – with Ara h 2 and Ara h 6 of peanut and Cor a 14 of hazelnut,
- Ses i 6 – with Ara h 3 of peanut and Jug r 4 of walnut [2].
Symptoms of sesame allergy
Sesame allergy can cause a range of symptoms: from skin to gastrointestinal to respiratory. The most common are:
- urticaria,
- abdominal pain,
- diarrhoea,
- vomiting,
- rhinitis,
- cough,
- wheezing [1].
Symptoms usually start to occur within 30 minutes of sesame ingestion. This type of allergy is also associated with a high risk of anaphylaxis. Statistics state that 70% of reactions to sesame meet the criteria for an anaphylactic reaction, and almost 50% of these lead to hospitalisation [1]. The diagnostic criteria for anaphylaxis include:
- sudden onset and rapid progression of symptoms
- life-threatening disorders (concerning airway patency, respiration, circulation),
- changes on the skin or mucous membranes (urticaria, erythema, angioedema) [8].
The prevalence of sesame allergy ranges from 0.1% to 0.9% (depending on the local diet) [1]. More than half of people with this allergy are also allergic to peanuts and tree nuts (e.g. hazelnuts, walnuts) [1,2]. Allergy to sesame often also co-exists with allergy to eggs or dairy, as well as other allergic diseases, e.g. atopic dermatitis (AD), asthma, allergic rhinitis [1]. Approximately 80% of allergic individuals are patients with multiple food allergies [1].
Sesame allergy in a child
Sesame allergy is one of the ten most common food allergies in children [5]. Once it occurs in childhood, it usually persists throughout life. Only 20% to 30% of children allergic to sesame develop tolerance over time [1,6]. Sesame allergy in children is better studied than in adults [1].
A study in Israel showed that 76% of paediatric patients had an allergic reaction after eating a sesame-containing food for the first time by the age of 2 years [6]. Characteristic for these children was an immediate reaction to a minimal amount of sesame [6]. Symptoms were first seen on the skin, followed by complaints from the respiratory and gastrointestinal systems [6]. Behavioural changes such as irritability and crying were also observed.
In Poland, studies have been conducted on sesame and nut allergy in children aged from 4 to 36 months [7]. The researchers determined the exact timing of peanut, sesame and tree nut allergy symptoms during the first 3 years of life in high-risk children. They hypothesised that the prevalence of this type of allergy in high-risk children by the age of 6 months is 5% and reaches 20% by the age of 2 years [7].
Diagnosis and treatment of sesame allergy
Sesame allergy can be confirmed by:
- oral food provocation (under medical supervision),
- positive skin prick tests with sesame allergens,
- positive blood test for specific IgE.
People at high risk of an allergic reaction to sesame should avoid contact with this allergen and always carry adrenaline in an injector with them. They can use short-term medication if symptoms occur. Desensitisation, or oral immunotherapy, is also becoming an increasingly promising alternative. Although sesame immunotherapy is still in the research phase, according to scientific reports, it may be an effective form of therapy in the future [1,4].
Aleksandra Lipiec
_______________________
Translation: Julia Majsiak
