When a 12-month-old baby is irritable, cries a lot, and has small bumps on their body, it could be a sign of various things such as hunger, pain, fatigue, or discomfort. It's important to explore each of these possibilities to identify the cause of the crying. As for the small bumps, they could be heat rashes, which usually go away on their own when the baby is in a cooler environment. You can help soothe your baby by washing the affected area with cool water or applying cool compresses. If you're unsure about the bumps, it's a good idea to consult with a healthcare professional for guidance.