Keep a diary of what she eats and drinks to rule out any sensitivity to that.
Make sure she understands that she must wash her hands before she eats any food and also to always wash her hands after she has used the toilet.
Tell her not to pick up and eat any food products that have fallen on the floor and ground because they are then contaminated and cause the poorly tummy.
Even when she does not feel like eating, make sure she drinks plenty of fluids so she does not become dehydrated. Give her jello if she likes that (that will help with her fluid intake).
Make sure that any raw fruit and veg she eats is washed first.
Make sure she has a breakfast in the morning and also a good sleep pattern.
If you have a pet animal in the home, make sure she washes her hands after touching it and do not allow your child to be licked by a pet dog if you have one.
I would also check her out for parasitic worms to rule that out. I would also get some children's multi vitamins, the nice chewy ones, to give her one a day.
When she throws up, look at the vomit to see what it is she is bringing up. If there is a lot of phlegm that is discoloured, she may be ill from a throat infection.
Also observe her bowel movements, to make sure she does not have an obstruction.
Hope you find the cause soon so that she can stop this vomitting. At the age of 5 she should not be experiencing "growing pains". It is more likely a viral or bacterial infection somewhere in her body that is making her feel unwell.
If she goes to nursery or school, have a chat with them to see if the monthly vomitting may be related to psychological reasons.
Wishing her a speedy recovery.
I went through the EXACT same thing with my daughter starting age 5. Two miserable years of misdiagnosis. You're going to be shocked to hear this but it's migraines. Yup. Abdominal migraines - exclusive to children and frequently either resolves with puberty or morphs into the "typical" migraine without so much vomiting.
Because she was so young she didn't have the words to tell about all the other symptoms - sensitive to light, headache, etc. An unusual characteristic of abdominal migraines is the child becomes very pale with dark circles under the eyes. Your child too?
My child is on migraine medicine (Topamax), sees a neurologist and only has one migraine every 6 weeks or so. When she was 5 she had one AT LEAST one a week. Her #1 trigger is lack of sleep. She used to trigger from excitement too - even happy excitement like birthdays and sleepovers. When a migraine is coming the only thing to do is let her be in a dark room with no sound, light or movement. And of course the bucket at the bedside b/c there is no stopping the vomiting.
Just google "abdominal migraines" and get her in to a good pediatric neurologist. Good luck
Table 1.—International Classiﬁcation of Headache Disorders
Diagnostic criteria for abdominal migraine include the
A. At least 5 attacks fulﬁlling criteria B-D.
B. Attacks of abdominal pain lasting 1-72 hours.
C. Abdominal pain has all of the following characteristics:
1. Midline location, periumbilical or poorly localized.
2. Dull or “just sore” quality.
3. Moderate or severe intensity.
D. During abdominal pain, at least 2 of the following:
1. Anorexia. (won't eat)
4. Pallor. (very pale)
E. Not attributed to another disorder. History and physical
examination do not show signs of gastrointestinal or renal
disease or such disease has been ruled out by appropriate