Researchers followed teenagers who had cow’s milk allergies as babies to see if it affected their bones. They compared 43 teens with confirmed milk allergies, 38 teens whose milk allergies turned out to be false alarms, and 49 teens without allergies. The study found that teenagers who truly had milk allergies as babies had slightly weaker bones in their forearms and shins compared to the other groups. However, the differences were small, and scientists say more research is needed to understand if this really matters for kids’ health long-term.

The Quick Take

  • What they studied: Whether babies who have cow’s milk allergies develop weaker bones by the time they’re teenagers
  • Who participated: 130 teenagers (average age 17 years old, 62% girls) split into three groups: 43 with confirmed milk allergies from infancy, 38 whose milk allergies were ruled out, and 49 with no history of milk allergies
  • Key finding: Teenagers with confirmed milk allergies as babies had lower bone mineral density (a measure of bone strength) in their forearms and lower legs compared to other teenagers, even after accounting for exercise, vitamin D intake, and dairy consumption
  • What it means for you: If your child had a milk allergy as a baby, their bones may be slightly less dense as a teenager, but the clinical importance of this finding is unclear. Talk to your doctor about ensuring adequate calcium, vitamin D, and exercise—all important for bone health regardless.

The Research Details

This was a follow-up study of teenagers who had participated in a milk allergy testing study when they were babies (1999-2001). Researchers tracked down the original participants at ages 15-18 and compared their bone structure using a special type of X-ray called peripheral quantitative CT (pQCT), which measures bone density without radiation exposure like regular CT scans. They also measured body composition using bioelectric impedance analysis, which sends a harmless electrical signal through the body to estimate muscle and fat percentages.

The study was observational, meaning researchers watched what happened naturally rather than assigning people to different treatments. They carefully adjusted their analysis to account for factors that affect bone health, including sex, body weight, physical activity over the past 5 years, vitamin D intake from food and supplements, and how much dairy products each teenager consumed.

The bone measurements were taken at two locations: the distal radius (the larger bone in the forearm near the wrist) and the distal tibia (the larger bone in the lower leg near the ankle). These sites are commonly measured because they’re easy to access and reflect overall bone health.

This research approach is important because it follows real people over many years, allowing scientists to see if early milk allergies have lasting effects. By comparing three groups (confirmed allergy, false alarm, and no allergy history), researchers could separate the effects of having a milk allergy from other factors. Adjusting for exercise, vitamin D, and dairy intake was crucial because these factors strongly influence bone development, so the researchers could see if the milk allergy itself—beyond just eating less dairy—affected bones.

Strengths: The study used objective measurements (CT scans) rather than self-reported data, and researchers carefully controlled for multiple factors affecting bone health. The milk allergies were confirmed using gold-standard testing (double-blind placebo-controlled challenges) when participants were babies, reducing uncertainty about who actually had allergies. Limitations: The sample size was relatively small (130 total), which limits how confidently we can apply results to all teenagers. The study couldn’t prove cause-and-effect, only association. Some original study participants were lost to follow-up, which could introduce bias. The study included only teenagers with a history of atopic eczema, so results may not apply to all children with milk allergies.

What the Results Show

Teenagers with confirmed milk allergies had lower bone mineral density in their forearms compared to those whose milk allergies were ruled out. The difference was measured using Z-scores (a statistical way to compare individuals to healthy peers): the milk allergy group had a Z-score of -1.49 compared to -0.78 in the false alarm group. This means the milk allergy group’s bones were about 0.71 units lower on the scale.

When comparing the milk allergy group to teenagers with no allergy history, differences appeared in both the forearm and lower leg. In the lower leg, the milk allergy group had lower total bone mineral density (Z-score -0.05 vs +0.01) and lower trabecular bone mineral density—the spongy inner part of bone (Z-score +0.20 vs +0.51).

These differences persisted even after researchers accounted for exercise levels, vitamin D intake, dairy consumption, body weight, sex, and age. This suggests the milk allergy itself, rather than simply eating less dairy, may be associated with the bone differences.

The study found no significant differences in body composition (muscle mass versus fat mass) between the three groups. This was somewhat surprising because researchers expected that teenagers with milk allergies might have different body composition if they were consuming less protein and calcium from dairy products. The lack of difference suggests that teenagers with milk allergies were getting adequate nutrition from other sources.

Previous research has shown that cow’s milk allergies in childhood can affect nutrition and growth, but long-term effects on bone health in teenagers have been less studied. This research adds to growing evidence that early allergies may have effects that extend into adolescence. However, the bone density differences found here are relatively small, and it’s unclear whether they translate to increased fracture risk or other clinical problems. Some earlier studies suggested that children with milk allergies might have lower bone density, but this is one of the first to follow the same children into their teenage years.

The study followed only 81 of the original participants from the 1999-2001 study, meaning some people were lost to follow-up, which could bias results. The sample was small overall (130 teenagers total), making it harder to detect real differences and limiting how broadly results apply. All participants had a history of atopic eczema, so findings may not apply to children with milk allergies who don’t have eczema. The study measured bone density at only two locations (forearm and lower leg) rather than the whole skeleton. The researchers couldn’t measure bone strength directly—they measured density, which is related to but not identical to strength. Finally, this was an observational study, so it can show association but not prove that milk allergies caused the bone differences.

The Bottom Line

If your child had a confirmed cow’s milk allergy in infancy: (1) Ensure adequate calcium intake from non-dairy sources (fortified plant-based milks, leafy greens, fortified orange juice, almonds, tahini) or calcium supplements if recommended by your doctor—moderate confidence; (2) Maintain adequate vitamin D through sunlight exposure, fortified foods, or supplements—high confidence this supports bone health generally; (3) Encourage regular weight-bearing exercise (running, jumping, sports, dancing) which strengthens bones—high confidence; (4) Have your teenager’s bone health assessed by their doctor if concerned—moderate confidence this is warranted given the study findings. These recommendations apply whether or not your child had a milk allergy, as they’re important for all adolescents.

This research is most relevant to parents of teenagers who had confirmed cow’s milk allergies as babies, particularly those with a history of atopic eczema. Pediatricians and allergists should be aware of this potential association when monitoring long-term health. Teenagers themselves should know that if they had milk allergies, paying attention to bone health through exercise and nutrition is important. This research is less relevant to people whose milk allergies were ruled out or who never had milk allergies. It’s also less clear how it applies to people who developed milk allergies later in childhood rather than in infancy.

Bone health improvements from better nutrition and exercise typically take months to years to become measurable. If you implement recommendations now, you might see improved bone density measurements within 12-24 months, though the most significant benefits accumulate over years of consistent healthy habits. Peak bone mass is typically reached in the late teens to early 20s, making this an important time to build strong bones.

Want to Apply This Research?

  • Track daily calcium intake (target: 1,000-1,300 mg for teens) and vitamin D intake (target: 600-800 IU daily), plus minutes of weight-bearing exercise per day (target: 60+ minutes). Log these weekly to identify patterns and ensure consistency.
  • Set a daily reminder to consume one calcium-rich food or beverage at each meal. For teens with milk allergies, this might be fortified plant-based milk at breakfast, leafy greens or tahini at lunch, and fortified orange juice or almonds as a snack. Add a weekly ‘bone-building activity’ goal (sports, dancing, jumping rope, or running) for at least 3 days per week.
  • Monthly check-ins on calcium and vitamin D intake consistency, quarterly reviews of exercise patterns, and annual discussions with your doctor about bone health. If your teen had a milk allergy, consider asking their doctor about periodic bone density screening (DEXA scan) every 2-3 years during adolescence to monitor trends.

This research describes an association between early milk allergies and lower bone density in teenagers, but does not prove that milk allergies cause weak bones. The clinical significance of the bone density differences found is unclear—they may or may not affect fracture risk or long-term health. This information is for educational purposes and should not replace professional medical advice. If your child had a milk allergy or you’re concerned about their bone health, consult with a pediatrician or pediatric allergist who can evaluate your child’s individual situation, dietary intake, and overall health. Do not make significant dietary changes or start supplements without medical guidance.