Could these be microscopic bug bites or a rash?

[marywrathers]

Or hives?
My baby had his 2 month shots 1 week ago but yesterday had red areas scattered all over his body with his flesh/neutral skin color in the middle. You can see the blood pulsate underneath the center or flesh/neutral skin color b/c it turns colors to the rhythm of a heartbeat. They look like mosquito bites (some small and some large-sized). Then they die down and form red dots like acne. But, we don't have any mosquitos in the house. When I rub my finger across one it feels like a bump just like a mosquito bite. They show up on his feet, hands, arms, lower abdomen, armpits, sides of chest, upper back, 2 above his eye, under his chin, 1 on his forehead.

They don't look terrible now. It seems like they are still there, yet fade away after a couple of hours then a new one shows up in a different location.

I wanted to ask you all this before calling the pediatrician b/c I don't think this is an emergency. He has no fever. He has vomited 3x since the shots.
What do you think?

I forgot to add the lighter colored centers of the red areas that pulsate are either the shape of circles or streaks. The streaks are about 0.5-0.75" long. My husband thinks it is a heat rash. We use AC. If it were a heat rash why would they show up on his feet and hands too?
Do you think it is related to his immunizations?
I can email more pictures: ***@****

Also, if it's an allergic reaction to detergent, why would it be on his hands, feet, and face too? Why would one red area pop up then die down then another shows up in a completely different location, pulsates, then goes away.

[Dr_Aparna]

Hi,
Hives are an itchy skin rash -- red, raised bumps with a paler center - triggered by an irritant. They can show up anywhere on your child's body, from the skin to the inside of his mouth, and vary in size from 1/16 inch in diameter to many inches across. Hives, also known as urticaria or wheals, can pop up in one area, fade, and appear in a totally different place within a matter of hours. Studies show that 2 to 20 percent of children develop hives at one time or another. An episode of hives can be over in a few hours, but most take about 48 hours to completely disappear. Some stubborn cases may even last a few weeks.
Common triggers include food allergies, drugs, viruses, insect bites and stings, plants, exercise, heat, and cold. Unfortunately, finding the cause of your child's hives is rarely easy; many times, you and your doctor will be unable to identify the exact cause.
Some children are simply more susceptible to certain irritants than others. Their immune systems reacts more quickly -- sometimes even to substances that are usually harmless -- and attack what appears to be an invader. When this occurs, the immune system releases a chemical called histamine to combat the irritants. Histamine makes blood vessels in the skin leaky, and the fluid that escapes gets trapped in the lower level of the skin, causing the bumpy hives. Histamine also provokes the itchy feeling that accompanies hives.
Contact your pediatrician or call 911 immediately if your child has any of these symptoms:
•Hives in or swelling around the mouth
•Wheezing or difficulty breathing  
•Pale, clammy skin
•Confusion
•Hives or difficulty breathing after an insect sting.
You should also contact a pediatrician for a non-emergency appointment in these circumstances:
•Your child has been taking medication and develops hives or a rash.
•He has had hives in the past and they recur.
•An episode of hives lasts more than four hours.
•The hives are accompanied by a fever of more than 100 degrees Farenheit, abdominal pain, or painful, swollen joints. Those symptoms can be signs of infection or disease.  
You can use cool compresses or a cool bath to reduce irritation and itching, but since hives are a reaction to histamine, antihistamines are usually the most effective treatment. Benadryl (its generic name is diphenhydramine) is available over-the-counter in liquid and pills. Follow the dosing guidelines carefully (and contact your doctor for children under 2-years-old). Give Benadryl every 6 hours until the hives fade. Continue the medication, spacing the doses farther and farther apart, until you are sure the hives are no longer a problem.
Your pediatrician may also recommend hydroxazine (Atarax), a prescription antihistamine. (Let your doctor know if you're using any over-the-counter medications for the hives.) Be aware that antihistamines make most children a little drowsy.
ref:http://www.myonlinewellness.com/topic/hiveschild