One of the most comon and tell tale sign of acid reflus is projectile vomiting. The baby will not be able to hold down even one ounce of formula or breast milk. When the baby spits up, it can be curdled, and have a sour oder to it, (not that formula or milk doesn't already, but worse than normal,) and it will feel warmer than normal spit up. Another sign may be excessive saliva. They are not ready for teething yet, but have been "slobbering" more than usual. The need to want to suck on a pacifire or their fist is also and indication they have "heart burn."
If the vomiting doesn't cease with in the first month, take them to be checked for Acid reflux. This can lead to starvation. The baby gets calories and if they spit it all back up with in a couple of minutes, they aren't getting the calories and nutrition they need to grow.
If it goes untreated, they can start to lose or stop gaining weight, stop growing as they should, their eye color can stop changing from grey to thier primary color. Their diaper output can become scarce and you find they're diapers aren't as wet as they should be. If let progressed, they can stop crying, and giving up.
The reason I gave this information, is because i have personal experience with this disease. My youngest son had Acid Reflux to the point that he had stopped growing, crying and peeing very little. I was petrified. I kept getting, "he'll out grow it, just keep doing what your doing." from doctors, nurses and a nutritionist. I had changed bottles 5 times, and changed formula's 4 times. I was so desperate that i asked a doctor that looked at my inscions from surgery, and he told me to bring him to his office first thing in the morning. when he found out he was born a month early, and what was going on with him, and seen him spit up, he put him in the hospital for a week. There we discovered not only his reflux, but that he has a heart murmer. My son was dehydrated because he couldn't hold anything down, and they put him on fluids. He was put on 150mg, liquid zantac twice a day. And I was told to spoon feed him thick rice cereal made with apple juice, and he was put on NeoSure, a high calorie formula for premee babies. I am so thankful and blessed that he is going on 4 years now.
Join my group for mom's who were, or have a failure to thrive. I'm trying to raise awareness about it and it's severity. We as mother's need support for things we have no control over, and we tend to jump on the self loathing boat if our child(ren) struggle to keep healthy in the busy world we know today. We just want to show some support and help you cope and deal with some of the issues that cause thriving difficulties. please consider my group, cafemom.com/group/failuretothriveawareness