According to Dr. Breanne Hayes Haney - an allergy and immunology expert at the School of Medicine, West Virginia University, USA, allergies are the result of interacting between bacteria and the living environment.
In particular, couples with eggs have a significantly higher risk of similar allergies because they share up to 100% of their genetic code.
Allergies occur when the body's immune system overreacts to harmless substances such as pollen, pet dander or certain foods.
At this time, the immune system creates antibodies to attack substances that are considered dangerous. This reaction causes many symptoms such as sneezing, nasal congestion, itchy eyes, coughing and in severe cases, it can lead to anaphylaxis (a life-threatening condition), requiring emergency medical intervention with epinephrine.
Allergies can appear with outdoor factors such as pollen, grass, insect bites; indoors such as dust mites, animal fur or from foods such as cow's milk, peanuts, seafood... Food allergies currently affect about 4-5% of the population.
In some cases, the allergy may improve over time, but there are also people who carry it for life.
Studies have shown a clear link between twins and allergies. A study in Australia showed that about 6070% of twin couples with the same egg had an environmental allergy, with this rate significantly higher in twins with the same egg than in twins with other eggs.
Similarly, with peanut allergy (a common allergy), pairs of twins with eggs have a significantly higher similar allergy rate.
However, not all twin couples will experience the same allergy. Although genetic factors play an important role, the living environment will also have a significant impact.
"For example, if a twin grows up in rural areas, where it is exposed to a lot of pets, bacteria and fresh air - the other child lives in urban areas, and is regularly exposed to pollution and cigarette smoke, the risk of allergy between the two can be very different," Dr. Breanne Hayes Haney explains.
Therefore, twins can be allergic to the same thing, but not always. Allergies are a complex combination of genes and the environment, so each child, even twins, can still react differently.
Understanding the relationship between genetic and environmental factors not only helps explain why allergies occur, but also opens up a more effective direction in preventing and treating future allergic reactions.
