Antibiotics may not be necessary at this time. Clear – pulmonary embolism (clear to frothy); COPD chronic obstructive pulmonary disease (clear to gray); viral respiratory infection (clear to whitish and sometimes a hint of yellow); asthma (thick and white to yellowish). See also
Phlegm

References


== External links ==
They resulted in 122,000 deaths. Causes
An ILD may be classified as to whether its cause is not known (idiopathic) or known (secondary). Idiopathic
Idiopathic interstitial pneumonia is the term given to ILDs with an unknown cause. They represent the majority of cases of interstitial lung diseases (up to two-thirds of cases). They were subclassified by the American Thoracic Society in 2002 into 7 subgroups:
Idiopathic pulmonary fibrosis (IPF): the most common subgroup
Desquamative interstitial pneumonia (DIP)
Acute interstitial pneumonia (AIP): also known as Hamman-Rich syndrome
Nonspecific interstitial pneumonia (NSIP)
Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD)
Cryptogenic organizing pneumonia (COP): also known by the older name bronchiolitis obliterans organizing pneumonia (BOOP)
Lymphoid interstitial pneumonia (LIP)

Secondary
Secondary ILDs are those diseases with a known etiology, including:
Connective tissue and Autoimmune diseases
Sarcoidosis
Rheumatoid arthritis
Systemic lupus erythematosus
Systemic sclerosis
Polymyositis
Dermatomyositis
Antisynthetase syndrome
Inhaled substances (Pneumoconiosis)
Inorganic
Silicosis
Asbestosis
Berylliosis
Industrial printing chemicals (e.g. carbon black, ink mist)
Organic
Hypersensitivity pneumonitis (extrinisic allergic alveolitis)
Drug-induced
Antibiotics
Chemotherapeutic drugs
Antiarrhythmic agents
Cigarette smoking 
Infection
Coronavirus disease 2019
Atypical pneumonia
Pneumocystis pneumonia (PCP)
Tuberculosis
Chlamydia trachomatis
Respiratory Syncytial Virus
Malignancy
Lymphangitic carcinomatosis
Predominately in children
Diffuse developmental disorders
Growth abnormalities deficient alveolarisation
Infant conditions of undefined cause
ILD related to alveolar surfactant region

Diagnosis
Investigation is tailored towards the symptoms and signs. A proper and detailed history looking for the occupational exposures, and for signs of conditions listed above is the first and probably the most important part of the workup in patients with interstitial lung disease. Pulmonary function tests usually show a restrictive defect with decreased diffusion capacity (DLCO).A lung biopsy is required if the clinical history and imaging are not clearly suggestive of a specific diagnosis or malignancy cannot otherwise be ruled out.