Rosacea is a chronic inflammatory skin condition with exacerbations that may be triggered by heat1. However, there is limited data on seasonal variations of rosacea exacerbations. In this study we use real-time Google Trends data to examine seasonal variations in rosacea search queries in the United States (US) and United Kingdom (UK) and its relation to seasonal temperature variations.

Google Trends (https://www.google.com/trends/) is a resource that provides normalized search volume data for terms queried using Google. This technology has recently gained attention in dermatology to assess prevalence of tanning bed use and skin cancer in the US and the UK2.

Monthly data for search volume in the US and UK was extracted from January 2004 to March 2016. Search volume data is represented by a relative search volume index (SVI), which ranges from 0 (no searches) to 100 (peak search volume) relative to all searches on the topic. US national temperature data by month was obtained from the National Oceanic and Atmospheric Administration3, and for the UK from the Met Office, the UK's national weather service4.

The monthly SVI for “rosacea” queries and temperature data over time for the US is plotted in Fig. 1 and for the UK in Fig. 2. There is a clear and reliable trend, where search queries for rosacea peak in March-April and temperatures peak in July-August each year. We determined the rate of temperature change of each month to highlight the times at which the temperature fluctuated most rapidly. There was a significant Pearson's correlation in the US (r=0.57, p=1.02×10⁻¹³) and UK (r=0.43, p=4.78×10⁻⁸) for “rosacea” SVI and the velocity of temperature change, indicating a positive relationship: the faster the temperature changes, the more searches for rosacea (for this data, the critical value for the Pearson correlation at a significance of p=0.05 is 0.17, indicating correlations >0.17 are significant).

Our data suggest that abrupt changes in temperature lead to more rosacea interest and potentially a greater number of exacerbations. This interpretation is based on the assumption that increased rosacea interest, as evidenced by search queries, may be a surrogate measure of increased rosacea disease activity in the public.

There are many factors that might explain this observation. Patients with rosacea have higher cutaneous blood flow, increased diaphoretic events, and heightened sympathetic nerve activity during heating as compared to healthy controls1. This suggests that sympathetic hyperactivity during heating contributes to flushing and other rosacea symptoms. Furthermore, epidemiological investigations have demonstrated a close association between Demodex mite infestation and rosacea5. Demodex mite mobility and survival increases at higher temperatures, contributing to increased rosacea exacerbations as temperatures increase5.

These findings should be interpreted with caution, as our results are restricted to Google search engine data. Nonetheless, Google Trends is a powerful tool that provides real-time, immediate, and free temporal data. We show that seasonal variations in temperature correlate with rosacea search volume. With refinery, this technology can contribute significantly to epidemiological research and be used to detect potential seasonal variations in less commonly studied dermatological conditions.