Why does alcohol consumption exacerbate psoriasis and eczema? 为什么饮酒会加重牛皮癣和湿疹？
Inflammatory skin conditions like psoriasis and eczema involve immune system dysregulation and skin inflammation, which alcohol can worsen through various pathways. Facial flushing, capillary dilation, and other adverse effects from alcohol consumption are primarily caused by acetaldehyde accumulation, a metabolic byproduct of alcohol. After drinking, alcohol is metabolized in the liver by alcohol dehydrogenase (ADH), converting ethanol into acetaldehyde.
1. Facial Flushing and Capillary Dilation:
Acetaldehyde directly stimulates the release of histamines and other vasoactive substances, causing blood vessels, particularly capillaries, to dilate. This dilation leads to facial redness or flushing, as the blood flow near the skin’s surface increases. In individuals with ALDH2 deficiency, this symptom is often more pronounced and can occur quickly even with small amounts of alcohol. Capillary dilation and vascular changes promotes inflammation by elevating levels of pro-inflammatory cytokines like TNF-α, IL-6, and IL-17. These cytokines are also involved in the pathogenesis of psoriasis and eczema, and their increase can intensify skin symptoms, leading to more frequent flare-ups, redness, and irritation in affected areas.
2. Oxidative Stress and Skin Barrier Dysfunction:
Alcohol metabolism generates acetaldehyde and reactive oxygen species (ROS), which contribute to oxidative stress. This stress can disrupt the skin barrier, impairing its ability to retain moisture and resist irritants. For eczema, where barrier function is already compromised, this effect can lead to more severe dryness, cracking, and susceptibility to secondary infections. Psoriasis lesions may also become more irritated, leading to increased scaling and discomfort.
3. Immune Suppression and Infection Risk:
Chronic alcohol use can weaken the immune response, making the skin more susceptible to bacterial and fungal infections. For individuals with eczema or psoriasis, this can lead to secondary infections that worsen symptoms. Moreover, alcohol’s impact on immune function may delay healing and increase the likelihood of chronic inflammation in affected areas.
4. Increased Heart Rate and Blood Pressure Changes:
Acetaldehyde and other byproducts may also affect the cardiovascular system by stimulating the release of catecholamines, which increase heart rate. Additionally, these effects can lead to transient increases in blood pressure and a sensation of warmth or dizziness.
5. Headache, Nausea, and Gastric Irritation:
Acetaldehyde is also an irritant to the stomach lining, leading to nausea and discomfort. It can also cause headaches due to vasodilation in brain blood vessels and the activation of inflammatory pathways.
6. Long-term Effects and Potential Harmful Impacts:
Chronic alcohol use, especially when combined with high acetaldehyde levels, contributes to oxidative stress and inflammation in liver cells, which may lead to fatty liver disease, hepatitis, and eventually cirrhosis. Additionally, persistent capillary dilation can damage small blood vessels over time, causing broken capillaries in the skin, particularly in the face. Alcohol and acetaldehyde have also been classified as carcinogens, increasing the risk of cancers, especially in the esophagus and liver.
Overall, alcohol can exacerbate both the symptoms and the underlying inflammatory processes in psoriasis and eczema. Due to its multiple impacts on skin vascularity, inflammation, and immune response, alcohol is generally advised to be limited for individuals managing these chronic skin conditions.
炎症性皮肤病如银屑病和湿疹涉及免疫系统的失调和皮肤炎症，而酒精会通过多种途径加重这些反应。面部潮红、毛细血管扩张以及其他不良反应主要由乙醛积累引起，乙醛是酒精代谢的中间产物。饮酒后，酒精通过酒精脱氢酶（ADH）在肝脏中代谢，将乙醇转化为乙醛。
1. 面部潮红和毛细血管扩张：
乙醛会直接刺激释放组胺和其他血管活性物质，导致毛细血管扩张和面部潮红，因为血流增至皮肤表面。对于乙醛脱氢酶（ALDH2）缺乏者，这种症状会更加显著，即使少量饮酒也会迅速发生。毛细血管扩张通过升高TNF-α、IL-6和IL-17等促炎细胞因子来促进炎症，这些细胞因子参与银屑病和湿疹的病程，并可加重皮肤症状，导致更频繁的发作、发红和刺激感。
2. 氧化应激与皮肤屏障功能障碍：
酒精代谢会产生乙醛和活性氧（ROS），引发氧化应激，从而破坏皮肤屏障，降低其保湿和抵抗刺激的能力。对于屏障功能已受损的湿疹患者，此效应会导致更严重的干燥、开裂和感染风险。银屑病患者的皮损也可能更加受刺激，导致更严重的脱屑和不适。
3. 免疫抑制与感染风险：
长期饮酒会削弱免疫系统，使皮肤更易感染细菌和真菌。对于湿疹或银屑病患者，这可能会导致继发感染，加重症状。此外，酒精对免疫功能的影响可能会延缓愈合过程，并增加患病区域的慢性炎症。
4. 心率和血压变化增加：
乙醛及其代谢产物还会通过释放儿茶酚胺影响心血管系统，增加心率，并可能引发短暂的血压升高、发热或眩晕感。
5. 头痛、恶心和胃部刺激：
乙醛对胃黏膜有刺激作用，导致恶心和不适。它还可扩张脑部血管，导致头痛，并激活炎症通路。
6. 长期影响和潜在危害：
长期饮酒及乙醛水平过高会在肝细胞中引发氧化应激和炎症，可能导致脂肪肝、肝炎甚至肝硬化。持续的毛细血管扩张可能会损伤面部小血管。此外，酒精和乙醛已被列为致癌物，增加食道癌和肝癌的风险。
总之，酒精会加重银屑病和湿疹的症状及其基础炎症过程，影响皮肤血管、免疫反应和炎症。对于管理这些慢性皮肤病，通常建议限制酒精摄入。
Reference：
- Alcohol use and burden for 195 countries and territories, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016Griswold, Max G et al.The Lancet, Volume 392, Issue 10152, 1015 – 1035
- No level of alcohol consumption improves health. Burton, Robyn et al. The Lancet, Volume 392, Issue 10152, 987 – 988
