What is Peanut Allergy?
Peanut allergy is a type of food allergy that causes an immune reaction on exposure to peanuts. In some individuals, even the smallest amount of peanut exposure can result in a severe, life-threatening allergic reaction called anaphylaxis.
About 1-2% of the population is allergic to peanuts. If you have a close relative with a peanut allergy, your risk of being allergic to peanuts is 7%. So you are 14 times more likely to have a peanut allergy if you have a relative with peanut allergy. Non-identical twins in a fraternal twin pair had peanut allergies 7% of the time. Identical twins on the other hand, had the allergies 64% of the time, which indicates a strong genetic component in this type of allergy.
There have been multiple studies on peanut allergy, and the most likely cause for it is said to be genetic. Peanut allergy occurs when an individual’s body wrongly identifies the harmless protein in peanuts as a harmful substance and launches an immune attack against it. The chemicals released by the body’s immune system against the peanut protein trigger a range of symptoms. The contact with peanuts can be direct, indirect, or by inhalation.
Symptoms of Peanut Allergy
The allergic reaction occurs just minutes after exposure to peanuts in any form. Signs and symptoms of the allergy include:
- Skin rash, redness, hives
- Swelling may be seen in some cases
- Itching and tingling around the mouth and in the throat
- Shortness of breath, coupled with tightness in the throat
- A runny nose
In some cases, peanut allergy can be life-threatening and a medical emergency. This type of reaction is called an anaphylactic reaction. Symptoms of an anaphylaxis reaction due to peanut allergy include:
- Rapid pulse
- Sudden and rapid fall in blood pressure
- Constriction of airways, resulting in a suffocating feeling
- Throat swelling that makes it difficult to swallow or breathe
Evolution and Allergies
Peanuts are rich in proteins and are unconventional because they flower over the ground, whereas their pods containing seeds are present underground. This is why they are called a geocarpic fruit. Due to this nature of the peanut plant, the pods and seeds come in contact with many soil pathogens and pests, including the fungus Aspergillus. The seed proteins of peanuts are modified slightly when they come in contact with this fungus, in order to survive. These modified proteins in the peanut seed membranes trigger our body’s immune receptors and modulate the immune pathways to release IgE.
This evolutionary history can be explored further to understand how the humble peanut became one of “The big eight food allergens in the world”.
How Do Genes Influence Peanut Allergy?
HMGA2 Gene
The HMGA2 gene, or High Mobility Group AT-Hook 2, is responsible for encoding a protein that belongs to the non-histone chromosomal high mobility group family of proteins.
rs10878354 and peanut allergy
SNP rs10878354 is a G>A polymorphism located on chromosome 12 in the gene HMGA2 Gene. The presence of the G allele significantly increases the risk of developing peanut allergy.
ZFAT gene
Zinc Finger And AT-Hook Domain Containing or ZFAT gene encodes a protein that binds DNA and acts as a transcriptional regulator in the process of cell survival and cell death. It is also a susceptibility locus for autoimmune thyroid disease on chromosome 8.
rs4584173 and peanut allergy
rs4584173 is a T>C polymorphism that is located on chromosome 8. The presence of the T allele increases one’s chance of developing peanut allergy.
HLA-DRA Gene
Major Histocompatibility Complex, Class II, DR Alpha is a part of the HLA Class II alpha chain. This gene plays a prominent role in the immune system as it is entrusted with the responsibility to present peptides derived from extracellular proteins.
rs7192 and peanut allergy
rs7192 is one of the most strongly associated genetic polymorphisms with peanut allergy. Having one T allele increases one’s risk of developing peanut allergy by 1.7 times, whereas having two T (TT) alleles increases the risk by 3 times.
HLA-DQB1 Gene
The HLA-DQB1 gene is associated with asthma, a condition that is characterized by the release of IgE on exposure to trigger factors. The genes of the HLA family belong to the Major Histocompatibility Complex(MHC) locus, which are involved in antigen presentation to T cells.
It is also important to note that asthma and food allergies are linked.
rs9275596 and peanut allergy
rs9275596 is located between HLA-DQB1 and HLA-DQA2 on chromosome 6. Similar to SNP rs7192, rs9275596 is also associated with an increased risk of peanut allergy. Having a single C allele increases one’s risk of developing peanut allergy by 1.7 times, whereas having two ‘C’ alleles (CC) increases the risk by three times.
Non-Genetic Influences on Peanut Allergy
While genetics is claimed to be the main reason for peanut allergies, there are also other risk factors that have a significant effect:
- Allergies to other foods: If you are allergic to other food items, you are at an increased risk of peanut allergy too. It has also been observed that having hay fever increases one’s chances of developing peanut allergy.
- Past peanut allergy: Some kids who have had peanut allergy in childhood tend to outgrow them in adulthood. But, there are chances of the allergy recurring.
- Age: Food allergies are particularly common in infants and toddlers, and as they grow up, their body and body systems mature, and one is less likely to be troubled by food allergies.
- Atopic dermatitis: Having a dry skin condition called atopic dermatitis increases one’s chances of suffering from peanut allergy.
How To Manage Peanut Allergy?
Dietary recommendations
- If you are allergic to peanuts, you must stay away from all foods that contain or are prepared using peanuts or its products like peanut oil.
- When you pick packaged foods, read the label carefully to check for other products that can trigger an allergic reaction similar to peanuts. These include monkey nuts, peanut butter, peanut flour, mixed nuts, and peanut oil, to name a few.
- You must also avoid cold-pressed, expelled, and expressed peanut oil, as these can trigger peanut allergy too.
- It is also recommended to avoid other nuts, nut butter, and extracts to be 100% sure you are staying safe.
Lifestyle modifications
If you are allergic to peanuts, there may be some chance that you are allergic to other nuts or foods too. To avoid an untoward allergic reaction, here are a few lifestyle modifications that can come in handy:
- Be cautious and never assume that a food does not contain allergens. This will prompt you to ask at a restaurant before you order a dish.
- Make it a habit to read food labels and warnings as relevant information is usually mentioned on it.
- It is okay to say ‘no’ to a dish that you are unsure of at a party or social gathering if you suspect peanuts or other possible allergens are present in it.
- If you or your child is allergic to peanuts, always carry emergency medications. It is always better to be safe than sorry.
Summary
- A very common food allergy, peanut allergy, affects a significant segment of the population.
- It occurs when the immune system identifies peanut protein as a harmful entity and triggers an immune response against it.
- A few genes that have been identified to have strong associations with peanut allergy. There is a better understanding of how some people are at an increased risk of developing the condition while others are not.
- The best way to manage peanut allergy or any food allergy, for that matter, is to avoid such foods. It is also advisable to have emergency antihistamines on hand in case you encounter the allergen accidentally.
References
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6563476/
https://www.healthline.com/health-news/researchers-discover-peanut-allergy-genes#Pinpointing-peanut-genes
https://genetics.thetech.org/ask/ask224
