Is dangerous to skip all 3 meals?

My brother (20) is type 1. He’s been in such a bad mood since 8am today and he has not eaten breakfast, lunch or dinner or just even a snack. He just had water.

He’s been working on his room all day, setting up his new bed and TV and he has not taken 1 break. We tried to get him to talk and to eat and he refuses. It’s about 10pm right now and he just went to bed.

My mother is freaking out saying anything could happen. He won’t check himself or even tell us anything. How dangerous is it for him to skip all 3 meals today?