 Healthy subjects 8 per cohort will be randomized to either pre-treatment or no pre-treatment 4 per group. The initial cohort will receive pre-treatment with cromolyn sodium. Subjects will be followed for 2 weeks for safety and tolerability, undergo a 2 week washout period and then be assigned to the alternative treatment i.e., subjects who received cromolyn sodium prior to PUL-042 inhalation solution will not receive pretreatment and then followed for an additional 2 weeks. 