What kind of harm could come from chewing a lot of Carefree sugarless
gum?  Peppermint flavor in particular.  "A lot" means a full pack of
17 sticks or more in an evening.

I am not interested in comments on why someone should or should not do
this or a discussion of alternative oral entertainment.  I am interested only in
possible harmful effects to the mouth or any other part of the body.

Thank you,
Archae0pteryx

Hello again, Tryx. I've done some more prowling, and have turned up
some interesting things.

It appears that there are at least two formulations of
peppermint-flavored Carefree Sugarless Gum. One of these uses
saccharine and aspartame as sweeteners, and the other uses sorbitol (a
"sugar alcohol").

"Gum Base 
 Hydrogenated glucose syrup 
 Glycerin 
 Natural Flavor
 Artificial color
 Aspartame
 Sodium Saccharin"

Cyberpunks Snacks: Official Snack Report
http://snacks.cyberpunks.org/carefreepep.html

"Carefree Sugarless Gum Peppermint
 Sweetened with sorbitol"

CandyShoppe
http://www.candyshoppe.ca/shop/Diabetic_Sugarfree_Candies.htm

"Carefree 
 Sorbitol, Saccharin." 

UIC College of Dentistry: Different Chewing Gums' Ingredients
http://www.uic.edu/classes/peri/peri343/carilec4/xylit3.htm

As mentioned in the "Comments" section, sugar alcohols can cause
diarrhea in some people, so the sorbitol-sweetened Carefree might
possibly have an adverse health effect in that area.

Regarding the burning sensation that your friend experienced, this is
a long shot, but a substance used in gum base caused an inflammatory
reaction when injected under the skin of hamsters:

"Oral Surg Oral Med Oral Pathol. 1976 Oct;42(4):461-9.
Histocompatibility of polyvinyl acetate, an ingredient of chewing gum.
 Carpenter WM, Grower MF, Nash G.

The histocompatibility of polyvinyl acetate (PVA), an ingredient of
chewing gum, was evaluated from both a direct irritant (toxic
reaction) and an allergic (antigen-antibody) standpoint. Subcutaneous
injections in rats and topical application of hamster pouches were
utilized. Polyvinyl acetate was shown to cause a moderate to severe
inflammatory reaction when injected subcutaneously, which peaked at
day 7 and was minimal at day 42. The histologic appearance of the
hamster cheek pouch was not significantly altered by the PVA. Although
PVA has been used as a plasticizer in chewing gum, it was not possible
to induce any histologic changes in tissues which resembled the
specific changes present in atypical gingivostomatitis (plasma-cell
gingivostomatitis)."

PubMed: Histocompatibility of polyvinyl acetate
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1067547

Sensitivity to another gum base ingredient, chicle, is mentioned as a
possible cause of "burning mouth syndrome":

"Burning mouth syndrome (also called stomatopyrosis, stomatodynia, and
oral dysesthesia) occurs most commonly among women after menopause...
Sensitivities to certain foods and food additives, particularly to
sorbic acid and benzoic acid (which are food preservatives), propylene
glycol (found as a moisturizing agent in foods, drugs, and cosmetics),
chicle (found in some chewing gums), and cinnamon, may play some role.
Deficiencies of vitamins, including B12, folic acid, and B-complex,
can cause burning mouth syndrome. Iron deficiency has also been
implicated."

The Merck Manual: Mouth and Dental Disorders
http://www.merck.com/mmhe/sec08/ch110/ch110c.html?alt=pf

An article whose title is "Allergic gingivostomatitis (due to gum
chewing)" was published in 1971 in the Journal of Periodontology:

PubMed: Allergic gingivostomatitis (due to gum chewing)
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=5288565&dopt=Abstract

So, if the gum is causing the problem (a big "if"), it seems that the
most likely culprits are polyvinyl acetate and chicle, both of which
are used in gum bases. I have done a thorough search, and have not
turned up any additional evidence that other ingredients, in either
formulation of Carefree peppermint gum, might be implicated in causing
irritation to the mucous membranes inside the mouth, as in your
friend's case.

It is possible that the physical act of chewing the gum is eroding the
lining of the mouth in some way, but that's just speculation.

Here are a few articles about chewing gum:

Massachusetts Dental Society: And Now, a Little Something to Chew On
http://www.massdental.org/public/wordofmouth.cfm?doc_id=112

CoolQiz: How is chewing gum made?
http://www.coolquiz.com/trivia/explain/docs/gum.asp

Delta Dental: Gum Chewing: Helpful or Harmful?
http://www.deltadental.com/servlets/OralHealth/dgumchew.jsp

Jungle Gum: Gum Facts
http://www.junglegum.com/Joy/gumfacts.html

Google search strategy:

Google Web Search: carefree gum ingredients
://www.google.com/search?hl=en&q=carefree+gum+ingredients

Google Web Search: stomatopyrosis "chewing gum"
://www.google.com/search?hl=en&q=stomatopyrosis+%22chewing+gum%22

Google Web Search: gingivostomatitis OR stomatitis "chewing gum"
://www.google.com/search?hl=en&q=gingivostomatitis+OR+stomatitis+%22chewing+gum%22

Google Web Search: "burning mouth" chewing gum
://www.google.com/search?hl=en&q=%22burning+mouth%22+chewing+gum

I hope your friend finds some relief. If she is not willing to give up
chewing gum, the most obvious suggestion is to try another brand. And,
of course, she should visit her dentist frequently so that the
condition can be monitored.

Best,
Pink

Wonderful job, Pink.  Thank you very much for digging so deep.

Tryx

Frankly, I doubt that there are any real health concerns here.
Although this gum contains saccharine, which has carcinogenic
properties, a person would probably have to chew several thousand
sticks of the gum a day to significantly increase the risk of cancer.
It also contains aspartame, which gets some people up in arms, but
I've seen no compelling evidence that aspartame in reasonable
quantities is harmful to normal people who do not have
phenylketonuria.

Here is a rundown on the product that really runs it down:

http://snacks.cyberpunks.org/carefreepep.html

It can have a laxative effect.

The person has a burning sensation in her mouth on the side where she
chews.  Her dentist didn't find anything there before, but did
question her about an area of her gum that looked oddly textured.  Now
she says the burning seems worse and is constant rather than
intermittent, and she thinks her tongue is swollen on that side too. 
She wondered if long-time use of this fake-peppermint-flavored gum
could produce some sort of chemical effect, such as a mild acid burn.

I suggested quitting the gum for a while, but she took it up to get
over quitting smoking, and she doesn't want to stop if she doesn't
have to.

Pink, could any of the ingredients you found cause an effect like that?

Micksawyer, thanks for the additional info.  That point didn't come
up, so I don't know if it's a concern.

Thank you,
Archae0pteryx

The kinds of flavoring and coloring agents that they use in gum are
approved by the FDA, and I really doubt that they would cause the kind
of problem that you've described. It's possible to have an allergic
reaction to almost anything, of course, and such allergies can arise
suddenly.

The laxative effect mentioned by micksawyer-ga is a problem with gums
that are sweetened with "sugar alcohols" such as xylitol. Carefree's
peppermint flavor does not contain sugar alcohols.

Well, it sounds to me like you've answered this one, Pink.  I can't
take it much further than that.  So why don't you go ahead and post
your answer?

Tryx

Pink,

Thanks very much for all your thorough additional research.  You might
be onto something in the case of my relative in suggesting that there
could be an allergic reaction of some kind.  The "burning mouth
syndrome" information also may be pertinent.  At least it's something
she can ask her dentist about.

She says Carefree is the only kind of sugarless gum that does not get
stuck to her dentures.

Tryx

Tryx,

Many thanx for the five stars and the very generous tip!

~Pink

I think gum chewing can cause fillings to release mercury.

While it is possible that excessive gum-chewing might release mercury
from amalgam fillings, it is not likely that this would cause the
symptoms reported here. Mercury primarily affects the nervous,
digestive, and respiratory systems and the kidneys. It is not an
irritant of mucous membranes.

Well, if you're interested, it turns out that my relative had some
kind of abscess under a bridge.  Now, I don't know if *that* could
have been caused or exacerbated by the gum-chewing, but at least this
rules out direct irritation of the mouth by the product.  So it's not
the fault of the Carefree after all.

Why that condition wasn't detected on the prior visit to the dentist
is a separate question that has nothing to do with chewing gum.

All the posted information is still something for a heavy user to think about.

Archae0pteryx

Regarding the abscess, I came across this recently. I wonder whether
the gum-chewing could have been related to dryness of the mouth, and
it may actually have been the mouth dryness that led to the abscess:

"Certain medications can cause excessive mouth dryness (xerostomia).
If your mouth is very dry, it can cause the rapid formation of severe
dental cavities, which can kill the nerve of a tooth and lead to a
dental abscess. Dental problems caused by dry mouth may be prevented
by taking frequent sips of water, chewing gum, or sucking on sugarless
hard candy."

Quest Diagnostics: Abscessed Tooth
http://www.questdiagnostics.com/kbase/topic/mini/aa119477/overview.htm

Hmmm ... interesting, Pink, thanks.  I'll pass it on.

Tryx