I am Dr Shamoon. From the history of a direct fall from a bike followed by a dark patch on the thigh in a 70-year-old man, what you are seeing is almost certainly a bruise (contusion/haematoma) - blood that has leaked out of small injured vessels into the tissue under the skin - and not a "blood clot" inside a vein, and not a skin allergy or rash. That distinction matters: a bruise from trauma is superficial and resolves on its own over 2-3 weeks, changing colour from red-purple to blue-black, then greenish-yellow-brown as it clears. An allergic rash would be itchy, raised, more widespread and would not be confined to the impact site. The genuinely important issue at his age is what else the fall may have caused, and whether a bruise is expanding. A localised firm, tender, swollen lump means a haematoma that is collecting, and in an elderly person a thigh injury can also fracture the femur or cause deep muscle bleeding with significant blood loss - so pain on weight bearing, inability to walk, or a deformed/shortened limb must be checked with an X-ray. Also, if he takes aspirin, clopidogrel, warfarin or any blood thinner, or has liver disease or a low platelet count, bruising is larger and continues longer, and he needs a doctor's review rather than home care. A true deep vein thrombosis presents differently - diffuse calf or whole-leg swelling, tightness and warmth rather than a patch - and would need an urgent Doppler scan.

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Seems like a bruise, if no other symptoms present with it. Apply cold compression  2 to 3 times daily, it should fade and disappear within 7 to 10 days.

Avoid fried and spicy food Water intake more Green leafy vegetables more Fiber meal Walk Do connect and consult Will help you

Requires a proper assessment to understand the underlying cause and guide you. Please book a consultation for a detailed evaluation, personalized treatment plan and further advice.

Thrombophob gel two, three times locally.  After cleaning

Based on your history it's a contusion caused by trauma.may have pain. . Please explain if any itching/ accidentally noticed the same only after trauma..

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Can help you, kindly consult and provide detailed history for proper diagnosis and further management

Its more likely fungal infection

It more looks like fungal infection along with bruise. Bruise will subside on its own within a week or two.  You can apply thrombophlebin ointment over it for bruise. Is he on antiplatelets or blood thinners?? Then it will take longer duration to heal. If it's fungal infection, itching is present then consult me for personalized treatment

Kindly verify it with your father , did it develop only after fall or it was there before itself because due to image I think it’s look like tinea

If you would like to discuss your concern in more detail, please feel free to contact me on WhatsApp at eight six one nine six six nine nine zero six. Alternatively, you can connect with me through the Practo app for a detailed consultation

Need a few more details please consult for further evaluation and treatment

Need few more details for further evaluation. Please consult