Mixed up with “intolerance” and “sensitivity” – intolerance is a vague term for any kind of reaction, agnostic to cause (most commonly used for gastrointestinal symptoms); “sensitisation” has a specific meaning (see allergy diagnosis) so not to be confused. Allergy is where there is an immune mediated problem (based ideally on history and testing) – but sometimes hard to know the mechanism.
2 basic types of food allergy, you can have both at the same time – type 1 (IgE mediated), and non-type 1 (non-IgE mediated – possibly type 4 hypersensitivity).
Most commonly (in Scotland – but varies across UK, especially with different ethnic groups), and varies widely across the world):
- Milk
- Egg
- Peanut
- Tree nuts
- Legumes/Pulses
- Sesame
- Wheat
- Crustaceans/molluscs
- Various fruits
Birch pollen sensitization in Northern Europe changes the kinds of allergies you get – cross sensitivity with fruit and nuts (pollen food syndrome) – whereas in the rest of Western Europe you get more fruit and seed allergies based on LPS.
Allergy has increased over recent decades – “hygiene hypothesis” has now been developed further to address entire “exposome“. Eczema increases the risk of food allergies 6-fold, via genetic and environmental factors (esp filaggrin mutations, and IL-4 receptor alpha chain polymorphisms).
Hospital admissions for food allergy in the UK have increased 3 fold over the last 30 years, with the biggest increase in children [BMJ 2021; 372: n251]. In big English study of primary care records, estimated incidence of probable food allergy doubled between 2008 and 2018; prevalence highest in children under 5 years (4·0%). Rate in children aged 5–9 years 2·4%, 15-19 years 1·7%. In those with previous food anaphylaxis, only 64∙0% of children and young people had at least one prescription for adrenaline autoinjector, and only 50.3% had them on repeat. Adrenaline autoinjectors prescription was less common in those resident in more deprived areas. 93.3% of first health care encounters for children regarding allergy were in primary care, with 2.2% in emergency departments. Only 7.4% of children had been seen for allergy in a hospital clinic. 92.2% of children had only ever been seen for food allergy in primary care (and looking at those prescribed AAIs, 93.5% only ever seen in primary care!).[Lancet Public Health 2024, Paul Turner]
If you ask people about their children’s allergies, up to 28% of infants will report allergies! Lifetime and point prevalence of self-reported food allergy 20% and 13%, respectively – point prevalence of sensitization as assessed by sIgE stands at 17%, skin prick test 6%, and food challenge positivity 1%. Based on clinical history or positive food challenge, food allergies have increased from 2.6% in 2000–2012 to 3.5% in 2012–2021. Point prevalence for under 16s for self reported but physician diagnosed food allergy is 3.75%. Patterns vary across European regions but not in a consistent way. [Spolidoro and Venter 2022]
Having a child with a food allergy has a significant effect on the quality of life for the whole family. One study suggested that having a peanut allergic child had a worse effect on a family than having a child with diabetes, even though with diabetes you also have restrictions on eating and the potential for serious adverse events. A similar study found the same comparing food allergic families with families where a child had a rheumatological diagnosis. The main domains affected were social. Patient/parent feedback pretty consistent across the world however (although most studies done in Europe and English speaking countries), and across time:
- Parents lived in fear after the first reaction, often perceiving it as traumatic, and often feeling guilt too
- They tried to live an ordinary family life and had to learn how to be one-step ahead and understand early signs.
- The family’s social life was also influenced.
- Parents asked for support and information from health professionals
- More knowledge and skills increased parents’ confidence (and by implication quality of life – Knibb 2015)
Mothers tend to report greater impact on the child’s quality of life and experience more anxiety and stress than fathers. Mothers tend to shelter the child, whereas fathers more often express a desire to expand their child’s life, and these differences are often greater where parents are separated.
The concern for the child’s safety affected eating outside the home, with birthday parties and visits to peers’ homes particularly threatening. School and nursery are a major source of concern and often led to more parental work, preparing safe lunches.
Parents often felt they had to teach themselves about allergies, due to the lack of early information provided by health care, and then ended up having to teach family, friends and educational institutions too.
Adolescence is a particularly stressful time, as parents recognize the need for the child to become more independent, at the same time that the adolescent can see the parents as excessively controlling (at least with respect to peanut allergy). Supportive friends particularly important for adolescents.