Researchers studied 343 children with allergic rhinitis (hay fever-like symptoms) to understand if vitamin D levels affect how severe their allergies are. They found that children with lower vitamin D levels had worse allergy symptoms, especially if they were allergic to pollen or multiple things. When kids took vitamin D supplements for 12 weeks, their allergy symptoms improved significantly. This suggests that vitamin D might play an important role in controlling allergy severity in children, and doctors may want to check vitamin D levels when treating kids with allergies.

The Quick Take

  • What they studied: Whether children with low vitamin D levels have worse allergy symptoms, and if taking vitamin D supplements helps reduce those symptoms.
  • Who participated: 343 children between ages 2 and 18 who had allergic rhinitis (sneezing, stuffy nose, itchy eyes from allergies). The study looked at their vitamin D levels and tested which things they were allergic to.
  • Key finding: Children with lower vitamin D levels had significantly worse allergy symptoms. After taking vitamin D supplements for 12 weeks, their allergy symptoms improved noticeably. The connection was especially strong in kids allergic to pollen or multiple allergens.
  • What it means for you: If your child has allergies, their doctor might want to check their vitamin D level. Getting enough vitamin D through supplements or sunlight may help reduce allergy severity. However, vitamin D supplements shouldn’t replace other allergy treatments—talk to your doctor about the best approach for your child.

The Research Details

This was a retrospective study, meaning researchers looked back at medical records from children who visited a hospital in Turkey between 2019 and 2024. They collected information about each child’s vitamin D levels, which allergens they reacted to (tested through skin prick tests and blood tests), and how severe their allergies were. The researchers then followed up with some children after they took vitamin D supplements for 12 weeks to see if their symptoms improved.

The doctors classified allergy severity using standard guidelines called ARIA, which helps measure how much allergies affect a child’s daily life. They used statistical analysis to find patterns between vitamin D levels and allergy severity, and to identify which factors made allergies worse.

This study design is useful because it examines real-world patient data rather than testing in a lab. By looking at actual children with allergies and their vitamin D levels, researchers can see if there’s a real connection. The 12-week follow-up with supplements helps show whether vitamin D actually helps reduce symptoms, not just whether low vitamin D happens to occur with worse allergies.

The study included a reasonably large group of 343 children, which makes the findings more reliable. The researchers used standard medical tests to measure vitamin D and identify allergies, which are well-established methods. The study was conducted at a major hospital, suggesting good data quality. However, because this was a retrospective study (looking back at records), researchers couldn’t control all the factors that might affect results, such as sun exposure, diet, or other treatments children were using.

What the Results Show

The median vitamin D level in the children studied was 16.0 ng/mL, which is considered low (healthy levels are typically 30 ng/mL or higher). Children with vitamin D levels below 20 ng/mL had significantly worse allergy symptoms compared to children with higher levels.

The study found that children allergic to pollen, dust mites, and cat dander all tended to have lower vitamin D levels. Kids who were allergic to multiple things at once (called polysensitization) had particularly low vitamin D and more severe allergies.

Most importantly, when children took vitamin D supplements for 12 weeks, their allergy symptoms improved noticeably. This improvement was statistically significant, meaning it wasn’t likely due to chance. Children also had fewer allergy-related eye symptoms (allergic conjunctivitis) after vitamin D supplementation.

The study found that older children tended to have lower vitamin D levels than younger children. Children who had both allergies and allergic eye symptoms together had worse outcomes overall. The combination of low vitamin D plus being allergic to pollen or multiple allergens created the most severe allergy problems.

Earlier research suggested that vitamin D might help control immune responses in allergies, but the exact relationship wasn’t clear. This study provides stronger evidence that vitamin D deficiency is connected to worse allergies in children. The finding that vitamin D supplements actually reduce symptoms supports the theory that vitamin D plays an active role in controlling allergies, rather than just being associated with them.

Because this study looked back at existing medical records, researchers couldn’t control all the factors that might affect results, such as how much sun exposure children got, their diet, or other medications they were taking. The study was conducted in Turkey, so results might differ in other populations with different genetics or environments. The researchers didn’t have a control group of children who didn’t take vitamin D supplements, so we can’t be completely certain the improvement was due to the supplements alone. Some children may have received other allergy treatments during the study period, which could have also helped their symptoms.

The Bottom Line

If your child has allergies, ask their doctor to check their vitamin D level. If it’s low, vitamin D supplementation appears to help reduce allergy severity and should be considered as part of allergy management. However, vitamin D supplements should complement, not replace, other allergy treatments like antihistamines or nasal sprays. Confidence level: Moderate—this is good evidence, but more research is needed to confirm these findings in different populations.

Parents of children with allergic rhinitis should pay attention to this research, especially if their child’s allergies are severe or not well-controlled with current treatments. Children with allergies to pollen or multiple allergens may benefit most. This is less relevant for children without allergies. Anyone considering vitamin D supplements should discuss it with their doctor first, as the right dose depends on age, current levels, and other health factors.

Based on this study, children who took vitamin D supplements showed improvement within 12 weeks. However, individual results may vary. Some children might see benefits sooner, while others might need the full 12 weeks. It’s important to have vitamin D levels checked before starting supplements and rechecked after treatment to ensure the approach is working.

Want to Apply This Research?

  • Track daily allergy symptoms on a scale of 1-10 (sneezing, nasal congestion, itchy eyes) and log weekly vitamin D supplement doses. Compare symptom scores before starting supplements and every 2 weeks after to see if there’s improvement.
  • Set a daily reminder to take vitamin D supplements at the same time each day. Also log outdoor time and sun exposure, as this affects natural vitamin D production. Users can photograph their supplement bottle to confirm they’re taking the right dose.
  • Create a monthly summary showing allergy symptom trends alongside vitamin D supplement adherence. Set a reminder for the 12-week mark to reassess symptoms and plan a follow-up doctor visit to recheck vitamin D levels and adjust treatment if needed.

This research suggests a relationship between vitamin D levels and allergy severity in children, but it is not a substitute for professional medical advice. Do not start, stop, or change any allergy treatments or vitamin D supplementation without consulting your child’s doctor first. Vitamin D supplements should be prescribed based on individual blood test results and medical history. This study was conducted in a specific population and results may not apply to all children. Always work with your healthcare provider to develop an appropriate treatment plan for your child’s allergies.