The “atopic march”: eczema, food allergy, asthma and hay fever

If your baby has eczema, sooner or later you’ll probably come across the phrase “atopic march”. It sounds ominous, as if eczema were the first step on a road that leads inevitably to food allergy, asthma and hay fever. The reality is more reassuring and more interesting. Here’s what the idea means, what newer research says about it, and what you can actually do.

What is the “atopic march”?

“Atopic” describes an inherited tendency for the immune system to overreact to everyday things, which shows up as eczema, food allergy, asthma and allergic rhinitis (hay fever). The atopic march is the idea that these conditions tend to appear in a set order in the same child: eczema in infancy, then food allergy, then asthma and hay fever as the child grows.

A 2023 review in the journal Medicina describes how the concept grew out of population studies, and how it was once thought to be the main path by which allergic diseases develop. It’s a useful picture, because it captures something real: these conditions really do cluster together.

Is there really a link?

Yes, children with eczema do have a higher chance of the other conditions. The Medicina review summarizes several long-term studies:

• In one study, children with eczema had about three times the odds of developing allergic asthma, and about two and a half times the odds of hay fever, compared with children without eczema.
• In Canada’s CHILD study, which follows children from birth, three-year-olds who’d had eczema had a higher risk of asthma and hay fever.
• In another birth cohort study, children whose eczema started early and persisted had a higher risk of asthma by age six.

Food allergy fits the pattern too. The Canadian Paediatric Society notes that the infants most at risk of developing food allergy are those who already have eczema or another food allergy. The British Association of Dermatologists adds that in most children, eczema comes before food allergy, not the other way round.

So how strong is the “march” itself?

This is where the story changes. A link between conditions isn’t the same as a predictable sequence.

In 2014, researchers analyzed two UK birth cohorts with nearly 10,000 children, checking for eczema, wheeze and rhinitis at ages 1, 3, 5, 8 and 11. Using statistical methods designed to find patterns, they identified eight distinct groups of children. Only 3.1% of children followed a profile resembling the classic atopic march. As the authors put it, fewer than 7% of children with symptoms followed that path. Far more had eczema only (about 15%), and many had other combinations, such as persistent eczema with later hay fever, or wheezing that came and went.

That’s why researchers increasingly use the term atopic multimorbidity instead. The Medicina review concludes that the atopic march happens in only a subset of children, even though children with eczema are more likely to develop other allergic conditions. These conditions share underlying causes and often show up together, but in many different orders and combinations, and one doesn’t necessarily lead to the next.

For you as a parent, the take-home message is this: eczema in your baby raises the odds of other allergic conditions, but it doesn’t set your child on a fixed road.

Which children are at higher risk?

The Medicina review lists factors that studies link to a higher chance of developing more allergic conditions:

• eczema that starts at a younger age
• more severe eczema, which several studies found to be the strongest risk factor
• eczema that persists rather than clearing
• a family history of eczema, asthma or allergies
• changes in the filaggrin gene, which helps build the skin barrier
• being sensitized to several allergens, or already having another allergic condition

A leading explanation for the link is the skin barrier (the outer layer that keeps water in and irritants out). When eczema leaves it leaky, allergens can get into the skin and prime the immune system, which may then react elsewhere in the body. That idea is well supported for food allergy; for asthma, the review notes the mechanisms are still not fully understood.

What can parents do?

Here’s where the evidence is honest about its limits.

Introduce allergenic foods early. This is the step with the strongest support. The Canadian Paediatric Society recommends that babies at high risk, including those with eczema, be offered allergenic foods such as cooked egg and peanut at about six months and not before four months, then keep eating them regularly, a few times a week. The Medicina review notes that several randomized trials found early introduction of peanut or egg to high-risk infants can lower the risk of those specific allergies. Screening tests before introducing foods aren’t recommended. If your baby has severe eczema or has already reacted to a food, ask your doctor for a plan.

Treat eczema well. Since more severe and persistent eczema is linked with more allergic conditions, keeping it under control makes sense, and it matters for your child’s comfort anyway. Whether better eczema treatment prevents asthma or hay fever hasn’t been proven yet, so think of it as good care, not a guarantee.

Don’t count on moisturizing a newborn to prevent it. A 2022 Cochrane review found that daily moisturizing of healthy babies in the first year probably doesn’t prevent eczema, and its effect on food allergy is uncertain. The Medicina review describes the same mixed picture from large trials. Moisturizing is still essential for a baby who already has eczema.

Be cautious about other “prevention” claims. The Medicina review found no adequate evidence for hydrolyzed formulas, prebiotics or vitamin D supplements to prevent allergic disease, and none of the prevention approaches tried for asthma and hay fever, such as avoiding house dust mites early in life, have enough evidence for routine use.

When should you talk to your doctor?

• Your child reacts to a food with hives, swelling or vomiting (call 911 for any breathing trouble or swelling of the lips, tongue or throat).
• Your child wheezes, coughs at night or gets unusually breathless with play.
• Your child has a constantly runny or blocked nose, itchy eyes or sneezing fits.
• Eczema is severe, persistent or not improving with good daily care.
• You’d like help introducing allergenic foods to a baby with eczema.

The atopic march is a real pattern in the sense that eczema, food allergy, asthma and hay fever often travel together. But only a small share of children follow the neat sequence the name suggests, and most children with eczema never march anywhere. Focus on what helps now: treat the skin well, introduce foods like egg and peanut early and keep them in the diet, and bring any new symptoms to your doctor.