Effects of the COVID-19 pandemic on individuals with chemical intolerance.

Objective: The purpose of this study was to determine if the COVID-19 pandemic had differential effects on individuals with chemical intolerances (CI). CI is characterised by multisystem symptoms initiated by a one-time high dose or persistent low-dose exposure to environmental toxins including chemicals, foods and drugs. With an estimated 20% US prevalence, symptoms include fatigue, headache, weakness, rash, mood changes, musculoskeletal pain, gastrointestinal issues, difficulties with memory, concentration and respiratory problems, which are similar to COVID-19 and its sequelae.

Design: A US population-based survey involving 7500 respondents was asked if they ever had COVID-19, what the severity was, and if they had long COVID-19. CI was assessed using the Quick Environmental Exposure and Sensitivity Inventory.

Setting: The Center for Disease Control estimates that over 24 million have been infected with COVID-19 in the USA with over 6 700 000 being hospitalised and over 1 174 000 deaths. Other industrialised countries show similar numbers.

Results: Those in the High CI class reported a greater COVID-19 prevalence, symptom severity and long COVID-19 than in the medium and low CI groups (p<0.0001). These associations were independent of race, ethnicity, income, age and sex. However, there were significantly increased odds of COVID-19 severity among women and those over 45 years old. Asian individuals were least likely to have severe symptoms compared with white individuals (OR=0.53; 95% CI 0.35 to 0.79). Black/African American individuals reported a lower prevalence of COVID-19 than non-Hispanic whites. However, one interaction between CI and race was significant, African Americans with high CI reported greater odds (OR=2.2; 95% CI 1.15 to 3.16) of reporting COVID-19 prevalence. Furthermore, African American individuals had significantly greater odds of increased symptom severity.

Conclusion: Prior studies show higher risk for COVID-19 among older age groups, male sex, those with pre-existing comorbidities (eg, challenged immunities) and those from minoritised racial/ethnic groups. The results of this study suggest that those with CI be included in a high-risk group. Various risk subsets may exist and future investigations could identify different risk subsets. Understanding these subgroups would be helpful in mounting targeted prevention efforts.