Red dots on women’s arms for no reason may be caused by skin vascular nevi, allergic dermatitis, abnormal blood clotting function, etc. 1. Skin vascular nevus: the most common, most of them are caused by vascular system lesions and so on. Generally no treatment is needed, but you should pay attention to observe whether there is any increase in size or other discomfort. 2. Allergic dermatitis: For example, mosquitoes, mites and other bites on the arm have certain toxins in their saliva. The toxin will cause an allergic reaction to the skin, resulting in the appearance of red spots. 3. Abnormal coagulation function: such as thrombocytopenic purpura, etc., generally due to abnormal blood platelets or coagulation factor abnormalities, as well as capillary abnormalities and other reasons, resulting in the appearance of subcutaneous pinpoint hemorrhagic dots, generally pressure does not fade, so that the skin or mucous membranes are red or purple. When there are only a few red dots, pay attention to observation, if the number is large, does not subside for a long time, or the symptoms worsen, it is recommended to consult a doctor in a timely manner, follow the doctor’s instructions for further examination, under the guidance of the doctor to clarify the cause, and targeted treatment or therapy.