Differential Diagnosis for Spreading, Itchy Red Rash
- Single most likely diagnosis
- Contact dermatitis: This is a common condition characterized by an itchy, red rash that can spread from the initial site of contact. The patient's symptoms, such as the rash starting on the wrists and behind the ear, and then spreading to other areas, are consistent with an allergic reaction to a substance that came into contact with the skin.
- Other Likely diagnoses
- Atopic dermatitis (eczema): This is a chronic skin condition that can cause itchy, red rashes, and can be exacerbated by environmental factors or allergies. The patient's symptoms of a spreading rash and intense itching are consistent with eczema.
- Seborrheic dermatitis: This condition causes a red, itchy rash, often on the face, ears, and torso. While the patient's rash started on the wrists and behind the ear, it's possible that seborrheic dermatitis could be the cause, especially if the rash has spread to other areas.
- Urticaria (hives): This is a condition characterized by itchy, raised welts that can appear anywhere on the body. While the patient's rash is described as a spreading, red rash, it's possible that hives could be the cause, especially if the rash is accompanied by other symptoms such as swelling or difficulty breathing.
- Do Not Miss diagnoses
- Cellulitis: This is a bacterial infection of the skin that can cause redness, swelling, and warmth. If left untreated, cellulitis can lead to serious complications, such as sepsis or abscesses. The patient's symptoms of a spreading rash and a bump in the affected area could be consistent with cellulitis.
- Erythema migrans (Lyme disease): This is a condition caused by a tick-borne bacterial infection that can cause a characteristic "bull's-eye" rash. While the patient's rash is not described as having this characteristic appearance, it's possible that Lyme disease could be the cause, especially if the patient has recently spent time outdoors in an area where ticks are common.
- Rare diagnoses
- Pityriasis rosea: This is a rare skin condition that causes a characteristic rash with a "herald patch" followed by a wider rash. While the patient's symptoms are not entirely consistent with pityriasis rosea, it's possible that this could be the cause, especially if the rash has a distinctive appearance.
- Dermatomyositis: This is a rare autoimmune condition that can cause a rash, muscle weakness, and other symptoms. While the patient's symptoms are not entirely consistent with dermatomyositis, it's possible that this could be the cause, especially if the patient has other symptoms such as muscle weakness or fever.