Marshmallow (Althaea officinalis) is known for its mucilaginous qualities. Marshmallow — the herb, not the white puffy confection roasted over a campfire — has been used for centuries as both a food and a medicine with usage dating back to ancient Greek and Roman cultures. Its botanical name comes from the Greek word "altho," which means "to cure." The mucilage, or gummy secretion, in the leaves and particularly the root is helpful for soothing sore throats, chapped skin, and minor wounds. Marshmallow root has been used in preparations with other herbs for cough.

Marshmallow Research
J Physiol Sci. 2014 Jan 25.  Protective effects of Althaea officinalis L. extract in 6-hydroxydopamine-induced hemi-Parkinsonism model: behavioral, biochemical and histochemical evidence.

Adv Biomed Res. 2015. Bronchodilatory and B-adrenergic effects of methanolic and aqueous extracts of Althaea root on isolated tracheobronchial smooth rat muscle. The methanolic and aqueous extracts of Althaea root inhibited the tracheobronchial smooth muscle contractions of rats in a dose dependent manner, but B-adrenergic receptors do not appear to engage in this process. Understanding the mechanism of this process can be useful in the treatment of pulmonary obstructive diseases like asthma.

Open trial to assess aspects of safety and efficacy of a combined herbal cough syrup with ivy and thyme.
Forsch Komplementarmed Klass Naturheilkd. 2005.
Changes in the symptoms of cough after treatment with a combined herbal preparation containing dry ivy leaf extract as main active ingredient, decoction of thyme and aniseed, and mucilage of marshmallow root (Weleda Hustenelixier, new formulation) and its tolerability were investigated in an open clinical trial ('Anwendungsbeleg'). Conclusion: Considering the traditional use of ivy leaves, thyme herb, aniseed and marshmallow root in preparations for cough, the reduction in the symptom score as well as the good tolerability the investigated combined herbal cough syrup seems to alleviate cough in consequence of common cold, bronchitis or respiratory tract diseases with formation of mucus.

Antibacterial activity of medicinal plant extracts against periodontopathic bacteria.
Phytother Res. 2003.
This study was performed to evaluate the antibacterial activity of Althaea officinalis roots - marshmallow -  Arnica montana flowers, Calendula officinalis flowers, Hamamelis virginiana leaves, Illicium verum Hook. fruits and Melissa officinalis leaves, against anaerobic and facultative aerobic periodontal bacteria: Porphyromonas gingivalis, Prevotella spp., Fusobacterium nucleatum, Capnocytophaga gingivalis, Veilonella parvula, Eikenella corrodens, Peptostreptococcus micros and Actinomyces odontolyticus. The results suggest the use of the alcohol extracts of H. virginiana, A. montana and marshmallow for topical medications in periodontal prophylactics.

Inhibitory mechanism of an extract of Althaea officinalis on endothelin-1-induced melanocyte activation.
Biol Pharm Bull. 2002.
It is known that expression of endothelin-1 (ET-1) increases in the epidermis after UVB irradiation, and that this plays an important role during the induction of pigmentation both as a mitogen and as a melanogen for normal human melanocytes (NHMC). When ET-1 acts on NHMC via the endothelin B receptor (ET(B)R) on their cell surface, mobilization of intracellular calcium is induced, which is followed by activation of Raf-1 located upstream of mitogen activated protein kinase (MAPK). We have continued the search for new agent which inhibit this calcium mobilization and we have found that an extract of marshmallow has such an action. Taken together, these findings indicate that an extract of marshmallow inhibits both the secretion of ET-1 from NHKC and the action of ET-1 on NHMC mainly by suppressing the ET-1-induced calcium mobilization without the modification of IP3 production, which in turn suggests that this extract is a useful ingredient for a whitening agent.

Marshmallows cause an outbreak of infection with Salmonella enteritidis phage type 4.
Commun Dis Rep CDR Rev. 1996.
Thirty-six cases of Salmonella enteritidis phage type (PT) 4 infection, mainly in children, were notified in one local authority in the two weeks beginning on 23 October 1995. Twenty-four cases and 42 controls nominated by cases were included in a case control study, which showed a significant association between illness and the consumption of marshmallow confectionery from a bakery. S. enteritidis PT4 was isolated from samples of the marshmellow, and all isolates had the same plasmid and pulsed field gel electrophoresis profiles. The marshmallow had been made using raw egg white, which shows that not all caterers follow the Department of Health's advice.