Air carrier Captain reported that after arrival at the gate in a foreign country; Ground personnel in full hazmat suits boarded and sprayed unknown chemicals onto the cargo and galley areas. Flight crew experienced physiological reactions and were concerned over exposure to the chemicals.

Narrative

Upon arrival into ZZZZ at the gate with brakes set; crew waited for Ground staff in full hazmat suit to board as is procedure. Typically; when an Aircraft Y lands; the main cargo will be sprayed; door closed; and crews [will] wait on the upper deck for 30 minutes until the main cargo door or L1 door is opened. Being Aircraft X; this was not possible due to no access to the main cargo deck.Crew witnessed a Ground Personnel spray a chemical from a 5-gallon sprayer bottle straight into the cargo access door and galley area; including food service items - i.e.; cups and paper towels. Crew is unaware and uninformed as to the chemical composition of the mixture and whether it is safe to be exposed at this close of a proximity since historically; crews are allowed to stay [in other areas] on Aircraft Y while [the] spray dissipates and takes effect. This created a very uncomfortable and unnerving feeling amongst crew as it was a major safety issue - and especially that a chemical administered by staff in full protective gear was done in the proximity of crews who were only wearing basic masks.A call was placed to the Duty for clarity. However; the responses were limited and the onus fell back on the crew to investigate and acquire information about what we may have been potentially exposed to. We were sent an email prior to departure about the composition of the chemicals used; stating safe household items." However; none of these items in my opinion are safe for direct contact to skin. For example; PRODUCTS TO DUOETYL DIMETHAMPHETAMINE CHLORIDE AND DIANE C8-10 DIMETHYL AMMONIUM CHLORIDE. This is an excerpt from the email received listing chemical makeup. Captain and First Officer both had minor skin and eye irritation following the application of the spray; which was only mitigated by opening the flight deck windows; trying to dissipate the effects of the spray application.Crews need to also be protected with PPE and breathing equipment at the higher level than face mask and shields. Household chemicals like bleach and ammonia that are seemingly harmless have different adverse effects for different individuals and cannot be blanketly applied in close proximity of human beings. On Aircraft X; where it is NOT possible to isolate crew on the [aircraft] as aircraft is sanitized; it is necessary to allow crew to deplane as the [Ground staff] exercise their right to sanitize inbound cargo and airplanes. Crews were told that simple household chemicals are being used. However; everyone dispensing them are in full hazmat suits - it does not promote transparency and a sense of honesty. I understand the challenges presented by COVID-19. However; crews should not be subject to this type of exposure."