I was reading in Parents magazine (September 2013, p 66) about health news. A new study in Annals of Allergy, Asthma & Immunology found that dustless chalk contains casein, which may cause kids with milk allergy to experience asthma symptoms. The symptoms include coughing and shortness of breath.
Most sidewalk chalk is dustless, so check the label if your child has a milk allergy.
If you want to learn more about what this study found, check it out on the Allergic Living website.