How are traits inherited?
Alleles are forms of a gene, forms which can vary from person to person as genes are a combination of four amino acids in an order that forms a code of sorts. You receive an allele from each of your parents for that gene, and the combination of these two alleles is known as the genotype. How the genotype is expressed physically is known as the phenotype, such as your eye colour.
Certain alleles have a more dominant expression than others, and will suppress the expression of these other recessive alleles. Remember that each biological parent has two alleles inherited from their own respective biological parents, and as such, there are four possibilities to consider.
A brown eyed individual could have two brown dominant alleles, or a brown dominant and blue or green recessive allele. Both cases will most likely produce a brown eyed individual. However, an individual with blue or green eyes will most likely have two recessive alleles of that respective colour because there is no brown dominant to supersede the recessive allele. There are cases of phenotype expression that are highly unlikely, the type of surprising that makes the parents of the child question what their partner has been up to.
Genetic inheritance is not a simple topic to grasp, but an undergraduate professor of mine explained it more clearly with a simple analogy than any of the textbooks I perused. Each species has a respective book known as a genome that consists of smaller chapters known as chromosomes. In each chapter, there are paragraphs known as genes. Each sentence represents a single gene that has a certain sentence structure, much like the code of a gene. The sentence structure can be altered depending on what the author is trying to say, something the body treats as a codon. When we read from two books with the same writing, we will gain the same understanding, but when one book is more compelling than the other, we may be apt to express this understanding over the less compelling book.
Why is heredity a risk factor for allergies?
Research has shown that approximately 40 to 80% of those afflicted by allergic rhinitis or asthma have a positive family history where another member is affected by these conditions.
Speaking of the inheritance patterns from earlier, how likely is it that a child will develop allergic rhinitis based on their parents?
It's generally thought that 60 to 80% of children with biparental allergies will go on to develop an allergy condition of their own. This is significant compared to the 30 to 50% with a single parental allergy or the 12% with no positive family history.
Will the child have the same allergy as his parent?
Not necessarily. Just because the biological father had a shellfish allergy, does not guarantee that the child will too. The most significant trait passed down is a genetic predisposition to release an antibody known as immunoglobulin E (IgE) in response to innocuous allergens.
Does gender have any role?
A fairly recent study from 2013 analyzed 1,456 children at the ages of 1, 2, 4, 10, and 18-years. This included skin prick allergy tests at certain check-ins, as well as an IgE test. If the parent was affected by eczema, asthma, or other allergic disease, the risk was increased in the son(s) related to the status of the father while the risk was increased in the daughter(s) related to the status of the mother.
What can be done to reduce symptoms?
As a parent or guardian, one of the ways to reduce a child's lifetime risk of atopic and allergic disease is to expose them to a diverse set of foods early in life. Research has determined that low food diversity can place infants at a higher risk of hay fever by 6 months and at a higher risk of asthma, hay fever, and episodes of wheezing by 12 months. Additionally, women who consumed more nuts during pregnancy produced infants with a lower risk of developing food allergies to peanuts and tree nuts. It's important to watch for signs of an allergic reaction and respond accordingly.
Feel free to utilize symptomatic relief when needed. As noted, exposure to allergens during pregnancy may actually induce some protection in the infant. Allergy Relief is a homeopathic preparation of a variety of ingredients, including plants from the Asteraceae family, one of the most common flowering families in Canada. Those taking this product, experienced an 88.5% improvement in their allergy symptoms. As it's a homeopathic preparation, the product is safe for pregnant and nursing mothers.
Another option to consider is quercitin which works by stabilizing the membrane of mast cells which contain and release histamine during an allergic reaction. It is typically poorly absorbed on its own though and is often taken alongside bromelain to increase how much enters the system. Also have a discussion with your primary care provider when considering a new medication, supplement or herbal product.
References
https://www.jacionline.org/article/S0091-6749(05)80088-0/abstract
https://www.jacionline.org/article/S0091-6749(13)02990-4/fulltext
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1216071/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2805592/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3409323/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4415518/
https://www.ncbi.nlm.nih.gov/pubmed/24366539