Skin Pharmacol Physiol
Effects of Spaceflight on Human Skin
Árpád Farkas a Gergő Farkas b
aHautarztpraxis Glattbrugg, Glattbrugg, Switzerland; bIndependent researcher, Zurich, Switzerland
Received: December 15, 2020
Accepted: March 5, 2021
Published online: May 31, 2021
Árpád Farkas, arpad.farkasmail @ gmail.com
© 2021 S. Karger AG, Basel
Spaceflight · International Space Station · Microgravity ·
Astronaut · Skin · Immune system · Microbiome
During both short- and long-duration spaceflight, several
health problems can occur, including those of the skin. As-
tronauts in space and after returning to earth experience er-
ythematous, burning, itchy, dry, sensitive, and thinning skin.
Other skin problems, such as infections, abrasions, lacera-
tions, delayed wound healing, and accelerated skin aging,
are also common. Human skin is an ecosystem composed of
a wide range of habitats for bacteria, fungi, and viruses called
microbiome, which not only show a strong skin site-specific
preference but also serve as microbial fingerprints that are
highly unique to individuals. These human skin-associated
microorganisms make a substantial contribution to the mi-
crobial ecosystems that inhabit the closed environments in
space. On the other hand, human skin microbiome is also
subject to change during spaceflight, which may lead to skin
infections or the flare up of skin diseases. This review high-
lights some of the interactions between the space environ-
ment and the skin. © 2021 S. Karger AG, Basel
The International Space Station (ISS) is a large closed
habitable construct located approximately 400 km above
the earth. Various life support systems sustain conditions
for humans to work productively and safely. Air pressure,
temperature, humidity, and contamination must be kept
under control . The evaluation of the future of both
noncommercial and commercial human spaceflight in
low-Earth orbit, including long-range opportunities for
the ISS and other free-flying structures, is ongoing. Hu-
man missions are planned to return to the surface of the
Moon and to land on Mars. Microgravity environment,
high radiation levels, continuous work and stress aboard
the ISS, other free-flying structures, and spacecrafts are
the main factors affecting human health over a time span
of minutes to months. Spaceflight alters the cardiovascu-
lar, musculoskeletal, respiratory, vestibular, visual, and
immune systems . Simultaneously, astronauts face
neurocognitive and neuropsychological changes . Wa-
ter supplies on the ISS are very limited, and the methods
that astronauts use to maintain good hygiene in micro-
gravity are not the same as on earth. Astronauts, for ex-
ample, are unable to take a bath or a shower; therefore,
they keep their body clean by using wet tissues and they
Skin Pharmacol Physiol
wash their hair with a rinseless shampoo. They do not
have a washing machine and they cannot change their
clothes as often as on earth. These and other circumstanc-
es, such as temperature change, microgravity, radiation,
and direct impairing factors, very much affect their skin
health and lead to frequent skin impairments and skin
diseases. The human skin is host to a complex and rich
microbial community, called microbiome. Spaceflight is
associated with strong and specific microbiome altera-
tions. Understanding the nature of skin alterations and of
the microbiome is key to managing astronaut health and
maintenance of the ISS, other free-flying structures, and
spacecraft equipment. In this article, the main factors en-
countered in space and their impact on human skin will
Human Skin Impairments and Diseases during Space
Based on the medical records it seems that cutaneous
alterations represent a major concern for astronauts. Ery-
thema, peeling, dryness, burning, pruritus, sensitivity,
thinning, and delayed wound healing are frequent skin
problems [4–11]. Space suit, glove, boot, celestial dust,
and lunar soil can cause significant trauma to crew mem-
bers, such as irritation, bruising, and abrasion, and glove-
induced frostbite, ecchymosis, and onycholysis were re-
corded [12–16]. Skin diseases such as psoriasis, seborrhe-
ic dermatitis, atopic dermatitis, contact dermatitis,
folliculitis, rosacea, and acne may flare up [4, 8, 10, 17,
18]. Bacterial, fungal, and viral infections [9, 19–22] may
occur and reactivation of herpesviruses causing herpes
zoster was noted [4, 23] and increased incidence of hyper-
sensitivities and of allergies were documented  (Ta-
The National Aeronautics and Space Administration
(NASA) created the Longitudinal Study of Astronaut
Health in 1992 to address a variety of issues, including both
the health of astronauts during spaceflight and the longer
term health issues that might be associated with spaceflight
and flight training including the possibility that increased
exposure to radiation in space might have an impact on
skin cancer cases. The study found 33 cases of basal and
squamous cell carcinomas of the skin among 312 astro-
nauts compared to 27 cases among 912 controls, an almost
3-fold difference in rate, which is statistically significant.
All these cases of basal and squamous cell carcinomas of
the skin were excluded from the analysis of the astronaut
group and of the comparison group. The reason for this
deletion is that astronauts spend significant time outdoors
for both training and recreational purposes; therefore,
these results have to be interpreted carefully .
Skin Physiology in Microgravity: Dermal Atrophy,
Cutaneous Muscle, Hair Follicle, and Metabolic
During the SkinCare experiment, skin surface, epider-
mis, and dermis were analyzed preflight, in-flight, and
postflight of an ISS astronaut. One measuring field of the
2 inner forearms was treated with a skincare emulsion. It
seemed that after a prolonged stay in weightlessness, the
skin underwent an accelerated aging with a thinner, more
structured, coarser epidermis and a loss of skin elasticity.
These changes appeared to be reversible because after a
year the skin’s condition returned to normal .
Later the Skin-B project was launched to validate the
results of the SkinCare study on 6 astronauts. In orbit,
skin hydration, skin barrier function, and surface evalua-
tion of the living skin (SELS; VisioScan® VC98 camera)
were measured. On the ground, skin elasticity, skin den-
sity, skin thickness, and skin microcirculation were eval-
uated. An improvement was seen in skin hydration and
skin barrier function. No changes or improvement was
observed in the appearance of the skin surface. Skin den-
sity, skin thickness, and skin elasticity values were un-
Table 1. In-flight skin-related clinical symptoms and medical
conditions which may occur, flare up, or worsen on board the ISS
Clinical symptoms Medical conditions
Burning Seborrheic dermatitis
Pruritus Atopic dermatitis
Peeling Contact dermatitis
Thinning Bacterial infections
Abrasions Viral infections
Bruising Fungal infections
Fluid shift Hypersensitivities
Delayed wound healing
ISS, International Space Station.
Skin in Spaceflight
Skin Pharmacol Physiol
changed from preflight values. These findings correspond
to some reports from other astronauts after returning
from flight. Quicker skin healing, decreased skin cracking
over the course of the mission, and use of a lower amount
of skin lotion than on earth was documented. The authors
of the Skin-B investigation explain these differences by
improved space conditions such as the use of better exer-
cise devices and better nutrition on board the ISS .
During the Skin-B project, the authors measured the skin
surface profile by means of SELS and after interpreting
their results they concluded that it is necessary to take a
closer look at the fluid shift phenomenon when an in-
creased volume of fluid travels toward the upper regions
of the body, making them look swollen. They found that
only the parameter skin volume leads to meaningful data
under microgravity and the formulas for the SELS param-
eters, such as roughness, scaling, and wrinkles, need to be
reevaluated . These observations highlight the impor-
tance of carefully selecting and adapting the experimental
methods during microgravity studies.
A rodent study which involved 3 mice having spent 3
months in orbit showed a significant reduction in dermal
thickness accompanied by increased newly synthetized
procollagen. Transcriptomic data suggested that the der-
mal atrophy might be related to an early degradation of
defective newly formed procollagen molecules. Many
hair follicles in the growing anagen phase were observed,
validated by an increased expression of specific hair fol-
licle genes. Additionally the analysis of whole thickness
skin showed that a large proportion of the upregulated
transcripts encoded proteins related to striated muscle
In summary, data from the Skin-B study contradicted
the SkinCare results. During the SkinCare experiment, a
reduction in skin density, a loss of skin elasticity, and re-
duced skin thickness were observed. These skin physiol-
ogy parameters remained unchanged during the Skin-B
study and skin hydration and skin barrier function even
changed for the better. The above mentioned rodent
study confirmed the reduced skin thickness in agreement
with the data obtained in the SkinCare experiment. How-
ever, these changes should be the subject of further inves-
Another study which analyzed the hair follicles of 10
astronauts showed that genes related to hair growth, such
as Homo sapiens fibroblast growth factor 18, Homo sapi-
ens angiopoietin-like 7, and Homo sapiens cartilage oligo-
meric matrix protein, were upregulated during flight,
suggesting that spaceflight inhibits cell proliferation in
hair follicles .
A mouse study during a Space Shuttle Atlantis (STS-
135) mission showed that in the flight group many genes
responsible for regulating production and metabolism of
reactive oxygen species were significantly altered with
1.5-fold changes compared to controls. For extracellular
matrix profile, several genes encoding matrix and metal-
loproteinases involved in extracellular matrix remodeling
were significantly up-/downregulated. Of 332 biochemi-
cal markers, 19 differed significantly, with 12 upregulated
and 7 downregulated including altered amino acid, car-
bohydrate metabolism, cell signaling, and transmethyl-
ation pathways. The data demonstrated that spaceflight
condition leads to a shift in biological and metabolic ho-
meostasis as a consequence of increased regulation in cel-
lular antioxidants, reactive oxygen species production,
and tissue remodeling .
Environmental Biocontamination on Board the ISS
and Skin Microbiome
Diverse bacteria, fungi, and viruses inhabit the human
skin. These microorganisms have an individual pattern
and vary between different skin sites. Some microbes join
the ISS when new crew members or payload arrives and
some were inhabitants from the very beginning when the
station was assembled.
The initial colonization of surfaces on board the Rus-
sian segment of the ISS was dominated by Gram-positive
members of the genera Staphylococcus, Micrococcus, Ba-
cillus, and Streptococcus showing that the skin of crew
members was the primary source of early contamination.
Gram-negative bacteria and fungi were also present .
Predominant bacteria belonged to the members of the
Staphylococcus genus, isolated from 84% of air and sur-
face samples [31, 32]. In air samples, Aspergillus and Pen-
icillium were the dominant fungi, while on the surface
samples, Aspergillus and Cladosporium dominated [32,
33]. Similar observations have been made after sampling
of NASA’s Destiny Laboratory [34, 35] and Japan Aero-
space Exploration Agency’s Kibo facility aboard the ISS,
where earlier Alternaria and Malassezia species were also
Staphylococcus species isolated from ISS air and crew
members were resistant to at least 1 antibiotic used aboard
the ISS and most were capable of surface colonization and
subsequent biofilm formation . Rifampicin resistance
due to higher mutation frequencies of Staphylococcus epi-
dermidis cultivated in the ISS compared to ground con-
trols was confirmed during an investigation as part of the
Skin Pharmacol Physiol
SpaceX-3 resupply mission showing that the human
spaceflight environment leads to changes in bacterial mu-
tagenic potential . Many other studies were per-
formed, which analyzed ISS surface and air samples to
assess the succession and persistence of microbial com-
munities, their antimicrobial resistance profiles, and vir-
ulence properties. These investigations revealed the rich-
ness of microbial diversity inside the ISS and confirmed
previous results showing that skin-associated bacterial
and fungal species play an important role. Some of them
belong to risk group microorganisms showing antimicro-
bial resistance signatures associated with β-lactam, cat-
ionic antimicrobial peptide, and vancomycin. Prominent
virulence factors were cobalt-zinc-cadmium resistance
and multidrug resistance efflux pumps [40–50]. Table2
summarizes the most important skin-related microbial
species, which play a role on board the ISS.
One study has investigated the microbiome changes of
9 astronauts who spent 6–12 months in the ISS . The
ISS environment differentially influenced the forehead
and forearm skin microbiota. Alpha diversity and rich-
ness increased or decreased, depending upon the indi-
vidual, but was consistent between the forehead and fore-
arm skin. In spite of the bimodal variance amongst astro-
naut skin microbiomes, there was a common shift in the
microbial composition of all crew members. These chang-
es involved a significant in-flight reduction of Proteobac-
teria, mostly Gammaproteobacteria and Betaproteobacte-
ria, with a concomitant increase in Firmicutes, including
staphylococcal and streptococcal species. Different fac-
tors may contribute to the decreased amount of Gamma-
proteobacteria and Betaproteobacteria abundance such as
the lack of a “green” natural environment plus the con-
stant filtration of air and the alteration of the skin struc-
ture during spaceflight. The reduction of skin Gamma-
proteobacteria might then contribute to the high frequen-
cy of skin hypersensitivity reactions/rashes and skin
infections. The change in skin structure might also facili-
tate the establishment of skin infections by opportunistic
pathogens such as the staphylococcal and streptococcal
Human spaceflight activities in low-Earth orbit are in
transition as governments in the future become only one
of the possible customers for commercial services. There
is an emerging industry that is close to becoming a reality:
space tourism. In the near future, lunar surface opera-
tions and missions beyond cislunar space will help the
return of astronauts to the surface of the Moon and capa-
bilities are being developed for human missions to Mars
and other destinations.
Therefore, it is getting more important to better un-
derstand human health issues during these missions and
optimize healthcare in space, which includes optimal
body cleaning methods and the use of moisturizers, and
to address improper space suit, glove, and boot fit-in-
duced skin breakdown [15, 16]. In microgravity, desic-
cated skin particles or foot calluses simply float; therefore,
the station’s ventilation system should work properly.
The use of the NASA imaging systems facilitates the
diagnosis of health-related conditions and the crew’s sur-
geons periodically discuss all health issues of each crew
member to initiate a treatment with proper medication.
Telemedicine may function well for the astronauts on the
ISS, but as they get further away from Earth they will have
an increased communication delay so the approach to
medical care will need to change. Crews need to be more
autonomous and there needs to be a physician on board.
Skin cancer prevention studies have to be implement-
ed and the relationship between radiation and micrograv-
ity has to be further investigated. Common stick insect
(Carausius morosus) experiments showed abnormal dif-
ferentiation under space microgravity and recessive lethal
mutations were induced by space radiation in the prog-
eny of fruit flies showing that microgravity and space ra-
diation may together elevate mutation frequencies. It was
suggested that DNA damage repair inhibition and stress-
related protein accumulation were involved. On the con-
trary, some space experiments have shown that mutation
Table 2. Skin-related microbial species which play a role on board
Bacterial species Fungal species
ISS, International Space Station.
Skin in Spaceflight
Skin Pharmacol Physiol
frequencies and DNA repair activity were not affected by
microgravity in Escherichia coli, Bacillus subtilis, Dictyo-
stelium discoideum, Saccharomyces cerevisiae, and hu-
man cells. Measurements of space radiation in the Shut-
tle-Mir mission 9 showed that doses differed between tis-
sues and organs of the human body with effective doses
varying by 10% or more. There was a tendency to have a
high dose on the surface of the body (skin) and protrud-
ing near surface elements (e.g., bone surfaces correspond-
ing to the shoulder) and to have low doses in internal re-
gions (e.g., bone marrow and colon). These data highlight
the importance of radiation protection systems for travel
in space .
The dysregulation of the human immune system in
space includes altered leukocyte, monocyte, and granulo-
cyte function, altered cytokine production patterns, abro-
gated bone marrow responsiveness to colony-stimulating
factors, altered T-cell intracellular signaling, persistent
hypersensitivity reactions, inhibition of natural killer cell
activity, and apparent T helper 2 potential bias shift. This
means that astronauts are more susceptible to infections.
Interventions for reducing the risk of infections prior to
space journeys include vaccinations. Because of the pos-
sible reactivation of herpesviruses, varicella zoster virus
vaccine should be given to mention one. Screening of as-
tronauts for both methicillin-susceptible and methicillin-
resistant Staphylococcus aureus is worth considering and
Staphylococcus aureus carriers may be decolonized. Re-
cent research has demonstrated that colonizing the skin
and nares with extracellular serine protease-producing
Staphylococcus epidermidis selectively inhibits Staphylo-
coccus aureus nasal colonization and biofilm formation.
As such, a somewhat far reaching countermeasure could
involve colonizing astronauts’ skin and nares prior to
travel with extracellular serine protease-producing Staph-
ylococcus epidermidis [53, 54].
To mimic spaceflight conditions ground-based habi-
tats have been built such as the Antarctic Concordia Sta-
tion and isolation facilities like an inflated lunar/Mars
analog habitat, the Hawai’i Space Exploration Analog and
Simulation isolation habitat, and the Mars500 facility.
The Mars500 project simulated a crewed 520-day-long
return flight to Mars. Cultivation assays revealed a Staph-
ylococcus- and Bacillus-dominated microbial community
on various surfaces, with a microbial load that did not
exceed the allowed limits for ISS in-flight requirements.
Mainly the crew was responsible for microbial dispersal.
Opportunistic pathogens, stress-tolerant or potentially
mobile element-bearing microorganisms were prevalent,
while the overall microbial diversity dropped significant-
ly over time . It is therefore important for the ad-
vancement of spaceflight activities to properly govern mi-
crobial communities. Data from these ground-based fa-
cilities may help to estimate future risk of crewed
spaceflight, could facilitate the design of a more optimal
spacecraft mission, and can promote to choose appropri-
ate microbial monitoring methods and potential counter-
measures to ensure a microbiologically safe spaceflight
A recent NASA study, which compared the impact of
the spaceflight environment on a pair of monozygotic
(identical) twin astronauts, highlights the importance of
the measurement of the same variables in an astronaut
and in his Earth-bound twin, because previous studies
could not integrate simultaneous effects on multiple sys-
tems and data types in the same subject. One of the previ-
ous observations confirmed by this study was that some
physiological adaptations, such as headward fluid shift,
are rapid and reach a new steady state within days .
However, this fluid shift has an impact during measure-
ments on the parameter volume, skin roughness, skin
scaling, and skin wrinkles. This has to be taken into con-
sideration when methods such as SELS are being used
Further and ongoing tests on more subjects are needed
to minimize space-induced skin impairments. The pos-
sible lessons learned with space exploration will also have
an impact on human health on Earth. In fact, this is a pro-
ductive, cross-fertilized, endeavor in which studies per-
formed on Earth yield countermeasures for protection of
space crew health and space research is translated into
health measures for the Earth-bound population.
Conflict of Interest Statement
The authors have no conflicts of interest to declare.
The authors did not receive any funding.
Árpád Farkas performed a comprehensive literature search in
the databases, contacted experts, and wrote the article. Gergő Far-
kas suggested the structure of the article and corrected the article.
Skin Pharmacol Physiol
Data Availability Statement
The authors provided a systematic critical digest of English ar-
ticles using MEDLINE search (2000–2020). Additional informa-
tion, articles, publications, and abstracts were identified by reading
previously published reviews, by searching NASA databases and
using ResearchGate (1974–2020). Experts in the field were also
contacted. Search terms included space, spaceflight, astronaut, mi-
crogravity, international space station, ISS, skin, dermatology, mi-
crobiome, immune system, telemedicine, and teledermatology.
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