Hydrogen sulfide reacts with aqueous selenous acid to produce selenium disulfide:

  
    
      
        
          
            H
            
              2
            
            
              
            
          
          
            SeO
            
              3
            
            
              
            
          
          +
          2
          
          
            H
            
              2
            
            
              
            
          
          S
          ⟶
          
            SeS
            
              2
            
            
              
            
          
          +
          3
          
          
            H
            
              2
            
            
              
            
          
          O
        
      
    
    {\displaystyle {\ce {H2SeO3 + 2 H2S -> SeS2 + 3 H2O}}}
  Selenium disulfide consists of 8-membered rings.
Sycosis vulgaris  is a cutaneous condition characterized by a chronic infection of the chin or bearded region. : 252  The irritation is caused by a deep infection of hair follicles, often by species of Staphylococcus or Propionibacterium bacteria. Asymptomatic or painful and tender erythematous papules and pustules may form around coarse hair in the beard (sycosis barbae) or the back of the neck  (sycosis nuchae). See also
Folliculitis
List of cutaneous conditions


== References ==