Snopes has an article about those diapers here
To summarize the article, nearly all disposable diapers on the market today use the same sort of "Super Absorbent Material", which is a crystalline substance that simply absorbs massive amounts of water (turning it into a gel-like substance). This same kind of particle, also known as polyacrylate absorbents, are used across the board because they are VERY good at what they do - absorbing up to 100 times their weight in water - while otherwise being nearly completely inert (not reacting to anything else, basically).
"The safety of superabsorbent material has been proven in more than 450 consumer safety tests that have studied every way a person could come in contact with it - through skin contact, ingestion or even inhalation. Each study has consistently demonstrated the safety and efficacy of this material.
Such negative findings inevitably prompt howls of outrage from people along the lines of "How can you claim that all those parents were lying about what happened to their children?" But that isn't the case: no one is claiming that parents are fabricating such reports; the issue of one of confusing cause with effect.
Children can and do develop severe cases of diaper rash and symptoms resembling chemical burns for a variety of reasons independent of what type or brand of diaper they use. To assume that an observed rash or burn in a diaper-wearing toddler must be directly and solely related to the brand of diaper worn without reproducible confirmatory evidence is an example of the post hoc ergo propter hoc
As well, to believe that a particular brand of disposable diaper poses a general danger of severely burning children in its ordinary use requires the additional beliefs that major companies who have been in the disposable diaper business for many years have suddenly unleashed new varieties of those products on the market without conducting the minimal testing necessary to uncover such issues, that the source of the reported hazard is obvious despite the fact that in-depth testing by government regulatory issues can't uncover it, and that this looming danger threatens all children who wear a particular brand of disposable diaper even though only a relative handful of the millions of consumers who use the brand have reported such issues.
A much more logical belief is that such cases, while real, are coincidental or only indirectly related to the brand of diaper used. Children may receive rashes and burns from other external sources unknown to their parents, such as exposure to caustic substances. Children may experience severe allergic reactions to something they've been exposed to (inside or outsider of their diapers). Children may develop cases of diaper rash so severe that they resemble chemical burns just as a matter of course and not because of the brand of diaper they're wearing. Other contributory factors may also come into play that produce rash or burn-like effects in only a small number of cases, such as unrealized interactions with other household products (e.g., bleaches or cleaning agents), the content of a child's excretions, children being left with unchanged diapers for far too long, or children experiencing some other type of medical issue that creates or exacerbates symptoms.
Likewise, confirmation bias is strong in such cases. People report and pay attention to only those cases that fit the suspected pattern, while ignoring cases of parents who report the same symptoms even though their children don't wear the identified type or brand of diapers, or parents who use the identified type or brand of diaper with no problems.
Many explanations are possible for these types of phenomena other than the commonly attributed or seemingly obvious ones. As it did with Pampers, we suspect that may prove to be the case here
Read more at http://www.snopes.com/medical/toxins/huggies.asp#fHDjsh9s8ieVpqyT.99