撰文：張傑醫生
還記得大學時代看過一套很駭人的電視，這是關於類似伊波拉病毒如何在某一個地區傳染居民和外來人，並引致所有人死亡。劇中被感染的人，就算是初期，都必然有紅疹在身體出現。所以，不少人印象很深，疹就是代表嚴重的疾病。
其實這只說對一半，紅疹是一種病徵，可以是皮膚的毛病，或是全身性疾病的一個反應。皮膚疾病可以單純的皮膚敏感、蚊叮蟲咬、風癱、曬傷等。全身性的反應可以是藥物敏感、感染性、自體免疫力毛病等。之前所謂「一半是正確」，就是在全身性的反應中，有些較嚴重，有些是較輕微。
嚴重的例子是：
1. 藥物敏感：由於紅疹只是表徵，當中的反應可以很嚴重。所以，如果是這個情況，一般我們會更加小心處理和觀察。
2. 感染性（急性）：例如麻疹、水痘、手足口病、德國麻疹、腮腺炎待。這些病都是有高度傳染性的。同時有發燒的徵狀。所以，我們在擔心這個病的併發症外，也會擔心它會傳染他人。故此，要特別小心。
3. 自體免疫力疾病：例如紅斑狼瘡症、過敏性紫癜症等。由於這類情況會有較多全身性的併發症，所以治療目標並不是去治療紅疹，而是處理根本的病症。
Written by: Dr Cheung Kit
I remember watching a terrifying TV show during my college days. It was about how a virus similar to Ebola spread among residents and outsiders in a certain area, leading to everyone’s death. In the drama, people infected with the virus would inevitably develop red rashes on their bodies even in the early stages. Therefore, many people have a deep impression that rashes represent serious diseases.
In fact, this is only half true. A rash is a symptom that can be a skin problem or a reaction to a systemic disease. Skin diseases can be simple skin sensitivities, mosquito bites, shingles, sunburns, etc. Systemic reactions can be due to drug sensitivities, infections, autoimmune disorders, etc. The previous statement “half true” means that among systemic reactions, some are more severe, while others are milder.
Severe examples include:
1. Drug Sensitivity: Since a rash is only a sign, the reaction can be very severe. Therefore, if this is the case, we generally handle and observe with extra caution.
2. Infectious (Acute): For example, measles, chickenpox, hand, foot, and mouth disease, German measles, mumps, etc. These diseases are highly contagious and also present with fever symptoms. So, in addition to worrying about the complications of the disease, we also worry about it spreading to others. Therefore, special care is needed.
3. Autoimmune Diseases: For example, lupus erythematosus, allergic purpura, etc. Since these conditions can have more systemic complications, the treatment goal is not to treat the rash but to address the underlying disease.
那麼「另一半」不是嚴重的疹是甚麼呢？
1. 玫瑰疹：這是一種幼兒「專有」的紅疹。一定是在感染了某種過濾性病毒後的反應。每當這種疹出現時，燒已經完全退卻，也代表病情已經穩定下來。一般這些紅疹在身軀出現，之後散開到四肢和面部。由於不痕不癢，所以不用特別治療。
2. 痱子：這是由於汗腺阻塞的結果。多數是環境氣溫太高或是衣服穿得太多所致。雖然會有少許痕癢，但是始終不像濕疹般不適，所以也不是不嚴重的問題。另一方面，只要將患處的溫度降低，情況便會改善。
3. 嬰兒濕疹
雖然嬰兒濕疹都會十分痕癢，但它是有時限性的。一般由出生後一個月開始，並維持至六個月左右。而且它對藥物的反應良好(例如中等強度的類固醇藥膏)。所以，基本上只要父母願去正面處理，並跟從醫生的治療，便會有良好的反應。
所以，出疹並不一定要有大問題。但是，若果出疹時，同時出現發燒、全身性的病徵、精神狀態不佳時，這就代表最好早點找醫生看看會較好。
So what are the “other half” of rashes that are not serious?
1. Roseola: This is a type of rash ‘exclusive’ to young children. It is definitely a reaction after being infected with a certain filtrable virus. Whenever this rash appears, the fever has already completely subsided, which also indicates that the condition has stabilized. Generally, these rashes appear on the torso and then spread to the limbs and face. Since they are not itchy or painful, there is no need for special treatment.
2. Heat Rash (Prickly Heat): This is the result of blocked sweat glands. It is mostly caused by the environment being too hot or wearing too many clothes. Although there may be a little itching, it is not as uncomfortable as eczema, so it is not a serious problem. On the other hand, as long as the temperature of the affected area is lowered, the condition will improve.
Infant Eczema
3. Although infant eczema can be very itchy, it is time-limited. It generally starts from one month after birth and lasts until about six months. Moreover, it responds well to medication (such as medium-strength steroid creams). So, basically, as long as parents are willing to deal with it positively and follow the doctor’s treatment, there will be a good response.
Therefore, having a rash does not necessarily mean there is a big problem. However, if a rash occurs at the same time as fever, systemic symptoms, or poor mental state, it means it would be better to see a doctor sooner rather than later.
