HYDROXYZINE

What is hydroxyzine?

Hydroxyzine is an antihistamine that helps block H1 receptors, which stops histamine from being released in the body. It’s commonly prescribed to relieve allergy symptoms like itching and can also help with anxiety or make it easier to fall asleep. There are some over-the-counter antihistamines, like fexofenadine and loratadine, that tend to be less sedating.

What does hydroxyzine do in the body?

Histamine is crucial in how our immune system reacts, especially during allergic responses. It causes blood vessels to become more permeable (“leaky”), leading to swelling and redness. Antihistamines block these effects at the H1 receptors, which helps reduce allergy symptoms.

First-generation antihistamines, including hydroxyzine, can easily cross into the brain and affect central nervous system receptors. This leads to different effects compared to second-generation antihistamines, which primarily target receptors outside the brain.

How can hydroxyzine help in long-COVID?

For people dealing with long COVID, hydroxyzine might be helpful. After COVID-19, some patients experience an overwhelming immune response, often called a cytokine storm. This can also involve alterations in histamine levels as well [1]. Hydroxyzine helps manage this immune reaction, potentially leading to improvements such as reduced wheezing and better exercise tolerance [2]. Some reports suggest that using hydroxyzine for an extended period could help improve long COVID symptoms like exercise intolerance, chest pain, fatigue, and brain fog. While we need more research, early findings are promising [3].

There’s alson encouraging but limited evidence that antihistamines might help with other long COVID symptoms. For instance, a study by Glynne et al. showed that 72% of long COVID patients who took a combination of H1 and H2 blockers for at least four weeks noticed some improvement in various symptoms, although not in dysautonomia [4]. It also mentioned ongoing T cell issues in these patients, suggesting that antihistamines may play a role in modulating the immune response. However, since this study was observational, we can’t assume a direct cause-and-effect relationship.

Another study by Samimi et al. looked at people with COVID-19 who were using antihistamines and found no significant difference in their symptoms compared to those who didn’t use them for four weeks[5]. While this didn’t specifically focus on long COVID, it gives some background on how antihistamines treat COVID.

Overall, early evidence is that antihistamines may help with long COVID, but more clinical trials are needed to confirm this and establish treatment recommendations.

References:

1Eldanasory OA, Eljaaly K, Memish ZA, Al-Tawfiq JA. Histamine release theory and roles of antihistamine in the treatment of cytokines storm of COVID-19. Travel Medicine and Infectious Disease. 2020;37:101874. doi:10.1016/j.tmaid.2020.101874

2Mashauri HL. Covid‐19 Histamine theory: Why antihistamines should be incorporated as the basic component in Covid‐19 management? Health Science Reports. 2023;6(2). doi:10.1002/hsr2.1109

3Pinto MD, Lambert N, Downs CA, et al. Antihistamines for postacute sequelae of SARS-COV-2 infection. The Journal for Nurse Practitioners. 2022;18(3):335-338. doi:10.1016/j.nurpra.2021.12.016

4Glynne P, Tahmasebi N, Gant V, Gupta R. Long COVID following Mild SARS-CoV-2 Infection: Characteristic T Cell Alterations and Response to Antihistamines. Journal of Investigative Medicine. 2021;70(1):61-67. doi:10.1136/jim-2021-002051

5Samimi S, Nimrouzi M, Sousani M, Vazani Y. EXPRESS: Antihistamine and COVID-19 outcomes in outpatients. Journal of Investigative Medicine. Published online August 1, 2024. doi:10.1177/10815589241270449

Clinical Trials

Search for: Long COVID, Other terms: Histamine H1 Antagonists | Card Results | ClinicalTrials.gov