I have red bumps bigger than acne on my chest and neck.

I wouldn't break them open if they aren't acne. could it be a rash or reaction to something?

If these bumps are inflamed and deep then the chances are you may have had an allergic reaction to something. I would start by drinking plenty of water to see if you can flush the allergen out of your body. I would also take and anti histamine tablet to clear the allergy. If this step does not help then I would suggest that you make an appointment with the doctor to have the area properly diagnosed.

In the meantime you can apply Tea Tree Oil which will help with the inflammation and kill and infection that may be lurking inside the bumps. You can also use an Aloe Vera gel that will help to heal the skin.

Hope this answer helps, feel free to add clarification as I have subscribed to this question.

It's still possible the ailment is related to acne, but worse. If your lumps are large, painful, and filled with pus, they are probably boils or carbuncles (a network of large boils). These types of infections require more serious treatment to take care of.

If you notice a large rash spreading around them or the pain is intense, get straight to a doctor. Only a medical professional can properly lance and drain these pockets without doing more damage. It's important to reign in these infections the right way, since spreading the infection can result in blood poisoning.

As long as it's manageable at home, fall back to proven home remedies. Warm compresses, good hygiene, and natural cures like turmeric are a good way to attack them from all angles. If you can take medication orally and help bring the pustules to a head, you'll see the infection fade away far quicker than you think is possible. These techniques are often better than prescription drugs, and far cheaper to boot.