The appearance of bumps on your arm specifically when stressed could be related to a condition known as stress-induced urticaria or hives. This condition occurs when the immune system releases histamines and other chemicals into the bloodstream in response to emotional stress, leading to the formation of hives—raised, itchy welts on the skin.

Here are some relevant insights into this condition and components to consider:

1. Mechanism: Stress can trigger the release of neuropeptides and other factors that influence the immune system, causing the release of histamine from mast cells, leading to hives. These can present as red, raised bumps and are typically itchy.

2. Localization and Triggers: The fact that the bumps appear on a specific area like your arm might be due to localized sensitivity or mechanical pressure in that area, which is exacerbated by stress. This is known as dermographism or pressure urticaria.

3. Diagnosis: It is important to differentiate these from other skin conditions that can mimic hives or are influenced by stress, such as eczema or psoriasis. A healthcare professional can provide a thorough evaluation.

4. Management: Managing stress through techniques such as mindfulness, breathing exercises, or regular physical activity can help reduce symptoms. Over-the-counter antihistamines might also be effective in alleviating symptoms. However, consult with a healthcare provider for a treatment plan suited to your situation.

5. Monitoring and Consultation: Keeping a diary of when these bumps occur in relation to your stress levels and other potential triggers can provide valuable insight. Consult a dermatologist or an allergist for definitive diagnosis and tailored management strategies.

Remember, while stress-induced hives are common, other medical conditions might present similarly, so professional evaluation is recommended to rule out underlying causes.