What would cause a man to suddenly get red blotches on his chest stomach and arms?

Several medical conditions can cause red blotches on the chest, stomach, and arms, including:

1. Allergic Reaction: An allergic reaction to certain foods, medications, or environmental allergens like pollen or dust can lead to red, itchy blotches on the skin called hives.

2. Heat Rash (Miliaria): Excessive sweating in hot or humid weather can cause blocked sweat glands and lead to heat rash, characterized by small red bumps on the skin.

3. Drug Rash: Certain medications, such as antibiotics or non-steroidal anti-inflammatory drugs (NSAIDs), can cause a drug rash as a side effect.

4. Viral Infection: Viral infections, such as measles, rubella, or scarlet fever, can cause red blotches on the skin as part of their symptoms.

5. Bacterial Infection: Some bacterial infections, such as impetigo or cellulitis, can lead to red and inflamed areas on the skin.

6. Sunburn: Overexposure to ultraviolet (UV) rays from the sun can cause sunburn, resulting in red, painful skin.

7. Insect Bites and Stings: Bites from insects such as mosquitoes, bees, or wasps can cause red and itchy bumps on the skin.

8. Skin Diseases: Certain skin conditions, such as eczema, dermatitis, or psoriasis, can lead to red patches, scaling, and itchiness on the affected areas.

9. Stress: Stress can sometimes trigger or worsen skin conditions, including redness and inflammation.

10. Liver or Kidney Disease: In severe cases, red blotches on the skin can be associated with underlying liver or kidney disorders that affect the body's ability to eliminate toxins and waste products.

11. Autoimmune Disorders: Some autoimmune conditions, like lupus or vasculitis, can affect the blood vessels and cause red, blotchy patches on the skin.

It is important to distinguish between these conditions and seek medical attention if the blotches persist or are accompanied by other symptoms such as fever, rash spreading rapidly, difficulty breathing, or if the person is otherwise feeling unwell. Consulting a healthcare professional for proper evaluation and diagnosis is crucial to determine the underlying cause and receive appropriate treatment.