Seborrheic dermatitis: A common skin condition in elderly individuals, characterized by a macular red rash that can appear on the abdomen and wrap around laterally. The absence of itchiness or pain and the chronic nature of the condition support this diagnosis.

Contact dermatitis: A possible cause of a macular red rash, especially if the patient has been exposed to new soaps, detergents, or other substances that may cause skin irritation. However, the lack of itchiness or pain makes this diagnosis less likely.
Tinea corporis (ringworm): A fungal infection that can cause a macular red rash on the abdomen. However, this condition is typically accompanied by itchiness and a more distinct border.
Psoriasis: An autoimmune condition that can cause a macular red rash on the abdomen. However, psoriasis is often accompanied by other symptoms such as joint pain and nail changes.

Malignant melanoma: Although rare, a macular red rash on the abdomen could be a sign of malignant melanoma, especially if the rash is asymmetric, has irregular borders, or is changing in size or color.
Lymphoma: Cutaneous T-cell lymphoma (CTCL) can cause a macular red rash on the abdomen, and it is essential to consider this diagnosis to avoid delayed treatment.
Infectious causes (e.g., cellulitis, abscess): Bacterial or fungal infections can cause a macular red rash on the abdomen, and it is crucial to consider these diagnoses to provide timely treatment and prevent complications.

Erythema ab igne: A rare condition caused by prolonged exposure to heat, which can cause a macular red rash on the abdomen.
Mastocytosis: A rare condition characterized by an accumulation of mast cells in the skin, which can cause a macular red rash on the abdomen.
Sarcoidosis: A rare autoimmune condition that can cause a macular red rash on the abdomen, often accompanied by other symptoms such as lung disease or joint pain.