Oral complications during and after cancer treatment are common. A key role in maintaining oral health plays saliva. In the last decade numerous studies have investigated immunological biomarkers such as cytokines in saliva samples. In children, the few studies have investigated salivary cytokines (sCK) suggesting that these are associated with oral health (sCK). One study investigating sCK in adult oncology patients showed an association between Interleukin-6 (IL-6) and severity of oral chronic graft-versus-host disease (GVHD) in survivors of hematopoietic stem cell transplantation. Therefore determination of sCK concentrations may also be helpful for assessment of GVHD activity and other inflammatory processes in cancer patients. In pediatric oncology patients, to the investigators' knowledge, no study has so far investigated sCK concentrations as markers for oral or systemic health.

Oral complications are common during and after cancer treatment. Oral mucositis typically occurs during or immediately after chemotherapy and may lead to pain, oral and systemic infection, and nutritional compromise. Late effects of oral mucositis as a result of cancer treatment include an increased risk for dental caries, xerostomia and osteonecrosis. It has been recognised, that regular assessment of oral health, prevention and early treatment of oral mucositis decreases early and late complication rates.

Saliva plays a key role in maintaining oral health and reduced salivary flow contributes to acute disorders and long-term sequelae in oral health. Saliva is a complex fluid secreted by the salivary glands and the gingiva. In the last decade numerous studies have investigated immunological biomarkers such as cytokines in saliva samples. These studies included individuals with various oral and systemic diseases including oral cancer, oral caries, autoimmune and endocrine diseases, metabolic syndrome, chronic kidney disease and psychiatric illnesses.

In children, the few studies that have investigated salivary cytokines (sCK) suggest that these are associated with oral health (sCK). For example, one study in 114 healthy adolescent girls aged 11-17 years showed that sCK concentrations were generally not associated with levels in the serum . In addition this study also suggested that the sCK concentrations are age dependent.

However, a number of other studies suggest that sCK may also reflect systemic diseases such as shown in a study including 20 children aged 9-17 with allergies (including asthma, allergic rhinitis and eosinophilic esophagitis) showing that Th-2 cytokines were detectable in sCK.

One study investigating sCK in adult oncology patients showed an association between IL-6 and severity of oral chronic GVHD in survivors of a hematopoietic stem cell transplantation. Therefore determination of sCK concentrations may also be helpful for assessment of GVHD activity and other inflammatory processes in cancer patients. In paediatric oncology patients, to the investigators' knowledge, no study has so far investigated sCK concentrations as markers for oral or systemic health.

Inclusion Criteria:

• Children with confirmed haematological/oncological disease and necessity for radio-or chemotherapy
• Age > 4 and < 18 years.

Exclusion Criteria:

• patients, who already were treated with radio- or chemotherapy
• patients with current or previous (last 7 days) symptoms of a respiratory infection, rhinitis, bronchitis and tonsillitis
• children with an autoimmune disease
• Use of systemic antibiotics within the last 2 weeks.
• Use of antimicrobial mouth rinsing solution within the last 12 hours,
• any vaccination within the last 48 hours
• known allergy to paraffin.

• Children with a new haematological/oncological diagnosis
• admitted to the paediatric oncology ward at the UKBB
• who will require radio- and/or chemotherapy.

Healthy children who present at the Schulzahnklinik respectively Volkszahnklinik for a dental prophylaxis