Why Your Friend Can Pet a Cat and You Can’t Even Walk Into the Room

Spring rolls around and one person is sneezing through every outdoor plan while their partner doesn’t notice the pollen at all. It’s easy to assume allergies are just random bad luck — you got unlucky, they didn’t. But allergic conditions, from hay fever to eczema to specific food reactions, are shaped by genetics more heavily than most people realize, and not always in the ways you’d expect.

Some allergies turn out to be almost entirely genetic. Others barely are. That distinction is exactly what a genetics-focused allergy report is built to sort out.

The Report Decoder series

This is one in a series where we take the massive, genuinely complicated health reports that services like SelfDecode generate from a DNA sample, and translate them into something you can actually read in five minutes. No spreadsheets of gene variants, no clinical percentiles — just what the report is actually telling you, and why it matters. Explore the rest of the series here.

Today’s topic: the Allergies Summary report, which looks at your genetic predisposition across common allergic conditions like hay fever and eczema, specific food allergies, key immune markers like IgE and mast cells, and the underlying genes that drive allergic responses.

The part that surprised us: not all allergies are equally genetic

If you assumed all allergies are “just genetics” to roughly the same degree, the actual numbers tell a more interesting story. Some allergic conditions are among the most heritable traits in medicine. Others lean much more heavily on environment and exposure.

That gap between peanut allergy (up to 80% genetic) and milk allergy (around 15%) is a good reminder that “food allergy” isn’t one uniform thing genetically — different allergens trace back to very different combinations of causes, even though they can look similar from the outside.

How the report actually sorts your results

Instead of drowning you in raw data, a report like this sorts each trait into one of three lanes based on your genetic tendency relative to most people:

• More likely — your genetics lean toward a higher tendency for this
• Typical — your genetics land in the ordinary range
• Less likely — your genetics lean toward a lower tendency

It covers common allergic conditions like hay fever, eczema, asthma, hives, and allergic skin reactions; specific food allergies including peanuts, eggs, milk, and shrimp; immune markers like IgE and mast cell activity that drive allergic responses; and the genes — like HLA-DQ, IL4, and histamine receptor genes — that shape how reactive your immune system is in the first place.

The detail everyone should know before reading any genetic report

Here’s the part that doesn’t get said often enough: a “More Likely” result does not mean you’re headed for a diagnosis.

Even someone with a meaningfully elevated genetic tendency toward a rare condition is still, in absolute terms, unlikely to develop it — because the condition itself is rare across the whole population to begin with. A shift from “typical” to “elevated” on a rare condition can still land you at very low overall odds.

Where results like this tend to be more genuinely useful is the reverse case: if you’ve already noticed a pattern — reactions that seem to run in the family, symptoms that flare with specific foods or seasons — seeing which part of the immune system your genetics point toward (histamine signaling, IgE production, skin barrier function) can help frame a more targeted conversation with an allergist instead of guessing at triggers one at a time.

What a personalized version looks like

Everything above is the general picture. A personalized Allergies Summary report swaps out the general statistics for your actual results — pulled from your own DNA — across 22 individual markers, grouped into 4 categories: Allergic Conditions, Food Allergies, Allergy Markers, and Allergy Genes, covering genes like HLA-DQ, IL4, and the histamine receptor gene HRH1.

It also comes with a prioritized list of 50 diet, supplement, and lifestyle recommendations, ranked by how much evidence supports them and how relevant they are to your specific results — rather than a generic “avoid allergens” list that ignores your biology entirely.