Mounting evidence documents a stark correlation between income and health, yet the causal mechanisms behind this gradient are poorly understood. This paper examines the impact of access to expertise on health, and whether unequal access to expertise contributes to the health-income gradient. Our empirical setting, Sweden, allows us to shut down inequality in formal access to health care; we first document that strong socioeconomic gradients nonetheless persist. Second, we study the effect of access to health-related expertise – captured by the presence of a health professional in the extended family – on health. Exploiting “admissions lotteries” into medical schools and variation in the timing of degrees, we show that access to intra-family medical expertise has far-reaching health consequences, at all ages: It raises longevity, improves drug adherence and reduces the occurrence of lifestyle-related disease in adulthood, raises vaccination rates in adolescence, and reduces tobacco exposure in utero. Third, we show that the effects of expertise are larger at the lower end of the income distribution – precisely where access to expertise is scarcer. Unequal access to health-related expertise can account for as much as 18% of the health-SES gradient, and may thus play a significant role in sustaining health inequality.