In some cases, a leg rash may occur with symptoms that are related to other areas of the body including:
·Decreased appetite
·Flu-like symptoms (fatigue, fever, sore throat, headache, cough, aches and pains)
··Joint pain or achiness and swelling
·Numbness or burning in the lower legs and feet
·Red eyes
·Sneezing and runny nose
·Stress, anxiety or depression
·Symptoms of poor blood flow to the extremities (sores that do not heal, cold extremities, and muscle cramping)
·Unexplained weight loss
·Vomiting

In some cases, a leg rash may occur with other symptoms that might indicate a serious or life-threatening condition that should be immediately evaluated in an emergency setting. Seek immediate medical care in other words call an ambulance if you, or someone you are with, have any of these life-threatening symptoms including:

Bloody stools or urine that is bloody, red or pink
Chest pain, pressure or tightness
Difficulty breathing, wheezing, or shortness of breath
Fainting or change in level of consciousness
High fever (higher than 101 degrees Fahrenheit)
Rapid pulse
Severe headache or abdominal pain
Sudden swelling of the mouth, lips, tongue, face, or throat
Vomiting blood

Any of these symptoms does need to be acted on immediately.

Of course all this is the possible cause but it should be remembered that there are a lot of causes for a leg rash such as a wide variety of diseases and conditions, such as infection, inflammation, allergic reaction, parasite and insect bites, and autoimmune processes. For example, an acute leg rash that appears suddenly may be caused by an allergic reaction or sensitivity to a particular substance, such as poison ivy, hair waxing or shaving, or an insect bite.. I would be really interested to know how your dad is now?