Paying close attention to the appearance of your skin is not all vanity. In fact, early symptoms of some serious conditions are manifest on the skin. Rashes, redness, bruising and swelling can be signs of internal problems.The recent sea lice saw many swimmers experience itchy blisters. Local health authorities gave advice on how to treat the problem and said in most cases a visit to the doctor or hospital was not necessary.So when should you see a doctor for a skin problem? A Body & Soul reader recently took advantage of our partnership with Johns Hopkins School of Medicine and asked for advice on a severe skin eruption which local doctors had been unable to diagnose.The query led Body & Soul to Mary Sheu, assistant professor in the Department of Dermatology at Johns Hopkins School of Medicine.“Skin conditions that should alert someone to seek immediate attention include: any severe or widespread rash, especially if associated with blisters on the skin or mucous membranes, or rash in someone with a fever or someone who is not feeling well in general,” said Dr Sheu.She said any signs of infection including redness, tenderness, warmth or swelling with or without fever, should be seen by a physician.She also warned that any signs of the condition shingles also warrants immediate medical attention.“Signs of shingles include burning pain limited to one side of the head, trunk, arms or legs, usually radiating in a line, pain often is followed by a rash or blisters,” said Dr Sheu.And she said it’s important to seek medical attention as soon as possible in the case of shingles because treatment is most effective if it starts within the first few days of the onset of pain.New or changing growths, bumps, moles or dark spots on the skin can be a sign of skin cancer and, according to Dr Sheu, should be checked by a dermatologist.“A new growth or persistent pimple that is not going away after a couple weeks, or is enlarging, bleeding, itching, or hurting; a dark spot or mole (flat or raised) with irregular shape, [or] more than one colour, [a] very dark colour, or one that is rapidly enlarging, these could be a sign of melanoma,” she said.Anyone with non-healing sores on their skin or widespread or painful blisters should also seek immediate medical attention according to Dr Sheu.“Skin conditions that could be related to systemic problems, such as autoimmune problems like lupus, can start with a sun-sensitive rash on the face,” she said.“The skin is often a window into internal conditions and can help lead to earlier diagnosis of internal problems; rashes or skin changes that are not going away on their own should be examined by a medical professional.”