The cloth itself may be abrasive enough for some people
Secondary syphilis
Poor personal hygieneUncommon causes:

Autoimmune disorders such as psoriasis
Lead poisoning
Pregnancy
Repeated scratching on a particular spot
Lyme disease
Scarlet fever
COVID-19 (see Symptoms of COVID-19 § Other)

Conditions
Diagnostic approach
The causes of a rash are numerous, which may make the evaluation of a rash extremely difficult. An accurate evaluation by a provider may only be made in the context of a thorough history, i.e. medications the patient is taking, the patients occupation, where the patient has been and complete physical examination. Points typically noted in the examination include:

The appearance: e.g., purpuric (typical of vasculitis and meningococcal disease), fine and like sandpaper (typical of scarlet fever); circular lesions with a central depression are typical of molluscum contagiosum (and in the past, small pox); plaques with silver scales are typical of psoriasis. The distribution: e.g., the rash of scarlet fever becomes confluent and forms bright red lines in the skin creases of the neck, armpits and groins (Pastias lines); the vesicles of chicken pox seem to follow the hollows of the body (they are more prominent along the depression of the spine on the back and in the hollows of both shoulder blades); very few rashes affect the palms of the hands and soles of the feet (secondary syphilis, rickettsia or spotted fevers, guttate psoriasis, hand, foot and mouth disease, keratoderma blennorrhagicum);
Symmetry: e.g., herpes zoster usually only affects one side of the body and does not cross the midline.A patch test may be ordered, for diagnostic purposes.
Triheptanoin was also designated an orphan drug by the European Medicines Agency (EMA).Triheptanoin was approved for medical use in the United States in June 2020.The FDA approved triheptanoin based on evidence from three clinical trials (Trial 1/NCT018863, Trial 2/NCT022141 and Trial 3/NCT01379625). The trials enrolled children and adults with LC-FAOD. Trials 1 and 2 were conducted at 11 sites in the United States and the United Kingdom, and Trial 3 was conducted at two sites in the United States.Trial 1 and Trial 2 were used to evaluate the side effects of triheptanoin. Both trials enrolled children and adults diagnosed with LC-FAOD. In Trial 1, participants received triheptanoin for 78 weeks. Trial 2 enrolled participants from other trials who were already treated with triheptanoin (including those from Trial 1) as well as participants who were never treated with triheptanoin before. Trial 2 is still ongoing and is planned to last up to five years.The benefit of triheptanoin was evaluated in Trial 3 which enrolled children and adults with LC-FAOD. Half of the participants received triheptanoin and half received trioctanoin for four months. Neither the participants nor the investigators knew which treatment was given until the end of the trial. The benefit of triheptanoin in comparison to trioctanoin was assessed by measuring the changes in heart and muscle function. Names
Triheptanoin is the international nonproprietary name. References
Further reading
de Almeida Rabello Oliveira M, da Rocha Ataíde T, de Oliveira SL, de Melo Lucena AL, de Lira CE, Soares AA,  et al. (March 2008).