Objective We investigate the association between adult asthma and wealth, testing whether the disease impairs wealth accumulation (social selection model) or if wealth protects against asthma (social causation model). Methods We use the National Longitudinal Survey of Youth (n = 7,644) and linear and logistic regressions to estimate the association between wealth and asthma. Changes in relative wealth following an asthma diagnosis and asthma status by increases in wealth through inheritance provide evidence on the causal direction. Results Asthma, particularly severe asthma, is associated with lower wealth. Wealth ranking does not change after a diagnosis of asthma, but inheriting a substantial sum is associated with a lower risk of severe asthma. Conclusion Wealth appears to protect against severe asthma, supporting the social causation model of disease.