The Internet is a significant source of information for patients. According to the National Institutes of Health, patient education materials (PEMs) should be at or below an eighth-grade reading level. Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer that affects patients over 50 with rising incidence. Unfortunately, US adults aged 65 + have the least proficiency in health literacy. This study assessed the readability of online PEMs and factors that contribute to readability. We retrieved 50 PEM websites and extracted primary content. A readability software package calculated six readability statistics and generated a consensus standard readability. Overall, only eight articles had a standard reading level of eighth-grade level or below (16%). The median standard reading level was at the 11th-grade level. We also examined MCC PEMs from cancer treatment institution websites (N = 20). We determined whether they contained institution-specific information, meaning they contained text information about the institution-specific expertise and specialist team. Websites containing this information (N = 13) had a significantly higher reading level than websites that did not (N = 7) in five of six readability metrics (p < 0.05). We concluded that MCC PEMs with institution-specific information led to significantly higher reading level scores. We propose that such information may increase cognitive load, as patients are learning about their disease and treatment and contending with the institution-specific information. The Cognitive Load Theory principles of intrinsic load (learning the material relevant to the disease and treatment) and extraneous load (institution-specific information and increased reading level) are constrained by limited working memory. Working memory decreases with age; hence, the patient demographic most sensitive to increased extraneous load tends to overlap with that of MCC. As patients typically read pages linked from their search engine, we suggest moving institution-specific information to another page, separate from the PEMs.